Especially in the alliterative phrase (as) snug as a bug in a rug, and variants, phrases built on the pattern (as) snug as [animal name] (in —) mean in an extremely comfortable position or situation.
The earliest occurrences of this phrase that I have found are as follows, in chronological order:
1-: From A Woman Kilde with Kindnesse (London: Printed by William Iaggard, 1607), by the English playwright and poet Thomas Heywood (circa 1573-1641):
Ser. My mistris sends that you should make lesse noise, to lock vp the dores, and see the houshold al got to bed: you Ienkin for [t]his night are made the Porter, to see the gates shut in.
Ienk. Thus by little and little I creepe into office: Come to kennel my masters to kennell, tis eleuen a clocke already.
Ser. When you haue lockt the gates in, you must send vp the keyes to my mistris.
Sis. Quickly for Gods sake Ienkin; for I must carry them: I am neither pillow nor bolster, but I know more then both.
Ienk. To bed good Spiggot, to bed good honest seruing creatures, and let vs sleepe as snug as pigs in pease-straw.
2-: From Rump: Or an Exact Collection of the Choycest Poems and Songs Relating to the Late Times. By the most Eminent Wits, from Anno 1639. to Anno 1661. Vol. II. (London: Printed for Henry Brome, and Henry Marsh, 1662), by Alexander Brome (1620-1666), a royalist poet who wrote drinking songs and satirical verses against the Rump Parliament in England:
Rump Rampant, or the Sweet Old Cause in Sippets.
To the Tune of,
Last Parliament sat as snug as a Cat.
3-: From “a merry drinking song”, in Andronicus Comnenius: A Tragedy (London: Printed for John Starkey, 1664), by the English playwright John Wilson (1626-1696):
Fill: fill up the bowl;
And about let it trowl;
’Tis a magical spell against sorrow,
It makes a man sing,
It cares not a straw,
For the Justice, or his law;
It fears neither spies, nor reporters:
It makes all the house
Lye as snug as a mouse;
And a petticoate sleep without Porters.
4-: From The Observator of 11th March 1681, by the English author and press censor Roger L’Estrange (1616-1704)—(London: Printed by J. Bennet, for William Abington, 1684)—here, the noun form denotes the nest or lair in which a hare crouches:
WHIG. Come; I’le shew ye my study, Tory.
TORY. Why you have got a Brave Library here.
Wh. […] Here can I sit as Snug as a Hare in her Form, and Chat away a Winters Evening with a Good Fire, a Pipe, and a Friend, and never feel how the time spends.
5-: From the portrait of the Purser, in The Wooden World Dissected: In the Character of a Ship of War: As also, the Characters of all the Officers, from the Captain to the Common Sailor. […] The Seventh Edition (London: Printed for and Sold by the Booksellers of London and Westminster, 1760), by the English satirical writer Edward Ward (1667-1731)—this book was first printed in London in 1707:
He is lodged so far under water, that a bullet must be sent by particular providence, if it reach him. Thus, while others battle it aloft, he sits as snugg as a bee in a box, making his honey.
6-: From The Humours of Oxford. A Comedy (Dublin: Printed by S. Powell, for George Risk, George Ewing, and William Smith, 1730), by the English poet and playwright James Miller (1704-1744):
Ape. You saw him safe under Ground then?
Tim. Ten Foot deep, Sir—for I went with old Strip-Corps the Sexton, to take off the Holland Shroud, they were so foolish to bury him in, and there he lay as snug as a Maggot in a Nutshel.
7-: From The Usefulness of the Stage to Religion, and to Government: Shewing the Advantage of the Drama in all Nations since its first Institution (London: Printed for T. Cooper, 1738), by the English critic and playwright John Dennis (1657-1734):
In this upper Gallery, I have sometimes seen a sedate Clergyman, a stiff Quaker, a Desenting Parson, an Anabaptist Teacher, or a Popish Priest, set as snug as a S——w in Beans, who would not have been seen in the Pit for a hundred Guineas.
8-: From The Genuine Account of the Adventures of Mr. Richard Brown, and his Sister, both of Dorsetshire. With several Remarkable occurences [sic] which very lately happened, and were delivered to the Author, by a Person who was Witness of the whole Truth (London: Bailey, Printer, [1750?]):
The Servants were then running here and there, with merry Hearts and jolly Countenances, every one was busy in welcoming of Guests, and look’d as snug as new lick’d Puppies.
9-: From The British Hero and Ignoble Poltron Contrasted: Or, The Principal Actors in the Siege and Defence of Fort St. Philip, and the Mediterranean Expedition, Characteriz’d. With some Strictures on the French Proceedings in America. An Ode. With Historical Notes, explaining and verifying the most remarkable Transactions and Occurrences that happened during the Continuance of this Important Siege (London: Printed for J. Robinson, 1756):
Long was his Voyage, tho’ the Wind
Was all the way his constant Friend.
At fam’d Gibraltar he arrives,
With all his Fleet, and all their Lives;
No furious Storms, or rugged Rocks,
Had bruis’d his Ships with Thumps and Knocks.
Snug as a Bug was all on Board,
And safe the Adm’ral, on my Word.
10-: From Bob Binnacle’s Epistle to the Landmen, who cleared Decks on board the Play-House, Covent Garden, published in The Beauties of all the Magazines selected (London: Printed for T. Waller) of March 1763—reprinted from the Ledger:
I set as snug as a maggot in the bread-room.
11-: From The New Bath Guide: Or, Memoirs of the B—r—d Family. In a Series of Poetical Epistles ([London]: Sold by J. Dodsley; J. Wilson & J. Fell; and J. Almon, London; W. Frederick, at Bath; W. Jackson, at Oxford; T. Fletcher & F. Hodson, at Cambridge; W. Smith, at Dublin; and the booksellers of Bristol, York, and Edinburgh, 1766), by the English poet Christopher Anstey (1724-1805)—the noun hodmandod denotes a snail:
So they hoisted her down just as safe and as well
And as snug as a Hod’mandod rides in his Shell.
12-: From A Genuine Collection of the Several Pieces of Political Intelligence Extraordinary, Epigrams, Poetry, &c. that have Appeared before the Public in Detached Pieces; Now carefully selected together in one View, by an Impartial Hand (London: Printed for Thomas Butcher, and John Russell, 1766):
Some Folks still aver,
After this Mighty Stir,
That P—tt is become a meer Bath:
Says my good Lord of Ch—th—m,
By Jove I’ll have at ’em,
And humble them all in my Wrath.
E’en let them complain;
What they say is in Vain,
Once more I have got in the Steerage:
I’ll hug myself Close,
As Snug as a Mouse,
With my Pension, a Place and a Peerage.
13-: From A New Dictionary in French and English (London: Printed for J. Nourse, and S. Hooper, 1769), by Henry Fox:
Coq S (oiseau domestique) cock.
Il èst là comme un Coq en pâte, he is there in clóver or as snug as a hare in her form.
14-: From The Stratford Jubilee (1769)—as quoted by F. J. Furnivall in Notes and Queries (London: Published by John C. Francis) of 16th February 1889:
In 1769 in the comedy of ‘The Stratford Jubilee’ […], Act II. sc. i. p. 32. An Irish captain says of a rich widow, “If she has the mopus’s *, I’ll have her, as snug as a bug in a rug.”
* The obsolete noun mopus denoted a coin of small value (a halfpenny or a farthing), and, in the plural, money.
15-: From Genuine Anecdotes of a Scoundrel; Or, Memoirs of Devil Dick: A well-known Character. By an Invisible Spy (Birmingham: Printed by C. Earl, 1772):
Being (because he was obliged to be) in a skirmish that happened between the different armies, this gallant Hero, Falstaff-like, laid himself down among the wounded and slain, where he remained as snug as a bug in a rug, till the event was decided.
16-: From a letter that the American statesman, inventor and scientist Benjamin Franklin (1706-1790) wrote to Georgiana Shipley (1756-1806) from London on 26th September 1772 [misdated 1773]—source: The Papers of Benjamin Franklin:
I lament with you most sincerely the unfortunate End of poor Mungo: Few Squirrels were better accomplish’d; for he had had a good Education, had travell’d far, and seen much of the World. As he had the Honour of being for his Virtues your Favourite, he should not go like common Skuggs without an Elegy or an Epitaph. Let us give him one in the monumental Stile and Measure, which being neither Prose nor Verse, is perhaps the properest for Grief; since to use common Language would look as if we were not affected, and to make Rhimes would seem Trifling in Sorrow.
Alas! poor Mungo!
Happy wert thou, hadst thou known
Thy own Felicity!
Remote from the fierce Bald-Eagle,
Tyrant of thy native Woods,
Thou hadst nought to fear from his piercing Talons;
Nor from the murdering Gun
Of the thoughtless Sportsman.
Safe in thy wired Castle,
Grimalkin never could annoy thee.
Daily wert thou fed with the choicest Viands
By the fair Hand
Of an indulgent Mistress.
But, discontented, thou wouldst have more Freedom.
Too soon, alas! didst thou obtain it,
Fell by the merciless Fangs,
Of wanton, cruel Ranger.
Learn hence, ye who blindly wish more Liberty,
Whether Subjects, Sons, Squirrels or Daughters,
That apparent Restraint may be real protection,
Yielding Peace, Plenty, and Security.
You see how much more decent and proper this broken Stile, interrupted as it were with Sighs, is for the Occasion, than if one were to say, by way of Epitaph,
As a Bug
In a Rug.
And yet perhaps there are People in the World of so little Feeling as to think, that would be a good-enough Epitaph for our poor Mungo!
If you wish it, I shall procure another to succeed him. But perhaps you will now chuse some other Amusement. Remember me respectfully to all the [torn] good Family; and believe me ever, Your affectionate Friend
17-: From the following poem, published in The Stamford Mercury (Stamford, Lincolnshire, England) of 19th November 1772:
The Pastry Cook’s Shop.
A Descriptive Piece.
While the keen air invites to superior delights,
Our appetites prone to provoke;
How sweet is the smell, from each kitchen or cell!
Of Soup, how delightful the smoke!
Still to crown the Repast, that same Soup would you taste,
Ye Merchants, and Maidens, from church
In all its perfection, oh! bend your direction,
With speed towards Horton and Birch.
There’s Pease, Vermicelli, of Turtle a jelly,
With delicate Soup a la Reine;
Capillaire, Orgeat, Lemonade, and what-not
I’ll warrant you’ll go there again.
Crouds unnumber’d may come to the little back room,
Where of light there appears a faint gleam,
There you’ll all sit as snug as a bug in a rug,
And enjoy both the Soup and the Steam.
18-: From The Maid of the Vale: A Comic Opera of Three Acts. As performing at the Theatre-Royal, Smock-Alley. Translated and Altered from La Buona Figliola (Dublin: Printed by Caleb Jenkin, 1775):
I don’t know how it is, but there is a certain agreeableness about me that not a girl in the parish is able to withstand—witness poor Phillis, who before I had said three kind things to her, the blossom was caught as snug as a rat in a trap.
19-: From Prologue to the Lecture upon Heads, published in The Universal Magazine of Knowledge and Pleasure (London: Printed by John Hinton) of August 1780:
Watchmen asleep may lie as snug as foxes,
And snore away the hours within their boxes.
20-: From Reynard’s Brush Triumphant in Henrietta-Street, published in History of the Westminster election, containing every material occurrence, from its commecement [sic] on the first of April, to the final close of the poll, on the 17th of May (London: Printed for the Editors, 1784), by J. Hartley:
Old Blackbeard is steady, and thinks himself snug,
On the ladies relying, as bug in a rug;
Aye, let him alone, he’s not given to blush,
But smiles at the fair ones, who shake his long brush.
21 & 22-: The Scottish physician James Makittrick Adair (1728-1802) used the variant as safe as a bug in a rug in the following two texts:
21-: In the Preface to Unanswerable Arguments against the Abolition of the Slave Trade. With a Defence of the Proprietors of the British Sugar Colonies, against certain malignant Charges contained in Letters published by a Sailor, and by Luffman, Newton, &c. (London: Sold by J. P. Bateman, ):
It has become very much the Fashion of the present Day to catch the Eel of Science by the Tail; and though she is apt to slip through our Fingers, somewhat of the Flavour adhering to the excrementitious Mucus, which besmears the Surface, still remains. From this delectable Source, many ingenious and useful Labours are ushered to the Public: such are your tiny Volumes in every Art and Science for the Use of Children, of which even such grown Infants as the Parents, the Nurse-maid, the Footman, and the Cook, often experience the Benefit; and those learned Works of Compilation, which come out in Numbers; and as both those kinds of Erudition are the Noli me tangere of Critics, the learned Authors are as safe as a Bug in a Rug.
22-: In Anecdotes of the Life, Adventures, and Vindication, of a Medical Character, Metaphorically Defunct (London: Sold by J. P. Bateman, 1790):
Had you accepted his challenge, you might have saved your credit, and have been as safe as a bug in a rug.
23-: From Rosina: A Novel (London: Printed for William Lane, 1793), by the British author Mary Pilkington (née Hopkins – 1766-1839):
Your letter of the fifth instant came safe to hand. I was right glad to heere as the goode fammillie be so stoute and hartie—but as to the enquirys that they keeps a makeing about Miss Rosina, it’s all mere nonsence, for she’s as snug as a bug in a rug, and they may shake theire cap at her, ’till such time as she takes another crotchet to go home again, as she did to whisk away from them, for no one reason that I knows about under the sun.
24-: From The Swallow and Tortoise, published in Evenings at Home; Or, The Juvenile Budget Opened. Consisting of a Variety of Miscellaneous Pieces, for the Instruction and Amusement of Young Persons (London: Printed for J. Johnson, 1793):
“Since you and I last autumn parted,
I’ve been a precious sleeper,
And never stirred nor started,
But in my hole I lay as snug
As fleas within a rug;
Nor did I put my head abroad
Till all the snow and ice was thaw’d.”
25-: From A Sketch of the Campaign of 1793. Part II. In a Series of Letters, from One of His Royal Highness the Commander in Chief’s Aid-de-Camps on the Continent, to Miss Lucy Lovegrove, in England (London: Printed by T. Rickaby, for T. Cadell, Jun. and W. Davies, Successors to Mr. Cadell, 1795):
Head Quarters, Furnes,
August 21, 1793.
What honor, dear Lucy, your hero will gain,
At the close of this brilliant and glorious campaign!
And be womanish fears to your bosom a stranger;
Our laurels are gather’d with scarce any danger.
At Head Quarters, we’re living as warm and as snug,
To use an old phrase, as a bug in a rug.