The phrase to have a bee in one’s bonnet means to be preoccupied or obsessed with something.

This phrase is an alliterative and metonymic* transformation of the earlier one’s head full of bees, meaning scatter-brained, unable to think straight, as if bees are buzzing around in one’s head.

(* An alliteration: bee and bonnet have the same initial consonant. A metonymy: the bonnet, which covers the head, is substituted for the latter; the same metonymy is found in the French phrase travailler du chapeau, literally to work from the hat, meaning to be a bit nuts: chapeau is substituted for tête, head—cf. mad as a hatter.)

The image of one’s head full of bees is first attested in the Prologue to the eighth Book of Eneados (1513), a translation into Middle Scots of Virgil’s Aeneid by the Scottish poet and Bishop of Dunkeld Gavin Douglas (circa 1474-1522):

Quhat bern be thou in bed, with hed full of beys?
(What, man, rot thou in bed with thy head full of bees?)

The same image is found in Ralph Roister Doister (around 1552), by the English playwright, cleric and schoolmaster Nicholas Udall (1504-56):

Whoso hath such bees as your master in his head
Had need to have his spirits with music to be fed.

The phrase was proverbial when the English playwright and epigrammatist John Heywood (circa 1496-circa 1578) published A dialogue conteynyng the number of the effectuall proverbes in the English tounge, compact in a matter concernynge two maner of maryages (1562):

(modernised spelling)
And thus, seeming well-nigh weary of his life,
The poor wretch went to his like poor wretched wife:
From wantonness to wretchedness, brought on their knees;
Their hearts full heavy, “their heads be full of bees”.

His head is full of bees is also in A Collection of English Proverbs (1678), by John Ray.

A slightly different formulation appeared in The Whigs supplication, or, The Scots Hudibras (1657), by the Scottish satirist Samuel Colville (floruit 1640-80):

But bishops say such thoughts delude,
Which comes from brains which have a bee.

Although this may not prefigure the phrase to have a bee in one’s bonnet, in the poignant The Mad Maid’s Song, by the English poet Robert Herrick (1591-1674), it seems that the erratic, zigzagging flight of the bee represents the maid’s obsession with her deceased lover:

Good morrow to the day so fair;
Good morning, sir, to you;
Good morrow to mine own torn hair,
Bedabled with the dew.

Good morning to this primrose too;
Good morrow to each maid;
That will with flowers the tomb bestrew,
Wherein my love is laid.

Ah! woe is me, woe, woe is me,
Alack, and well-a-day!
For pitty, sir, find out that bee,
Which bore my love away.

Ile seek him in your bonnet brave;
Ile seek him in your eyes;
Nay, now I think th’ave made his grave
I’ th’ bed of strawburies.

Ile seek him there; I know, ere this,
The cold, cold earth doth shake him;
But I will go, or send a kisse
By you, sir, to awake him.

Pray hurt him not; though he be dead,
He knowes well who do love him;
And who with green turfes reare his head,
And who do rudely move him.

He’s soft and tender, pray take heed,
With bands of cow-slips bind him,
And bring him home; but ’tis decreed,
That I shall never find him.

In a letter to the Reverend Philip Doddridge dated 8^th March 1738, the Reverend John Barker attributed the phrase a bee in one’s bonnet to the Scots:

I suppose you have heard of Mr. Coward’s pranks. He has, as the Scotch call it, a Bee in his Bonnet.

In Scotland, the original sense of the word bonnet (that is, a soft round brimless hat for men) has been retained, whereas, in England, the word cap had superseded bonnet in this sense by the 18^th century. For example, an anonymous English traveller wrote, in 1704:

I minded that most of the men, especially the meaner sort, wear thrumb caps in Scotland, which they call bonnetts.

 

The image of the bee can be compared to that of the maggot, found for example in Women Pleased (around 1619-23), by the English playwright John Fletcher (1579-1625):

Are you not mad, my friend? […] Have not you Maggots in your braines?

And A New General English Dictionary (1735), by Thomas Dyche and William Pardon, has the following:

Maggot: a small worm that breeds in nuts, &c. also a whimsical fellow, that is full of strange freakish fancies.
Maggottiness: a fulness of maggots, as cheese, a dead dog, &c. also that airy, changeable, whimsical, unsettled disposition of mind that is continually pursuing some odd or foolish device.
Maggoty: whimsical, unsettled, freakish, foolish, changeable, &c.

In Dictionnaire françois-anglois et anglois-françois (1776), Louis Chambaud translated the English phrase What maggot bites you? as Quelle fantaisie vous prend?, literally What whim takes you?.

In the same sense, French has the phrase Quelle mouche vous a piqué?, literally What fly has stung you?.

Similarly, the German word Grille, meaning a cricket, is also used figuratively to mean a whim. In Christian Ludwig’s German-English dictionary (1808 edition), Grille was translated into English as cricket and as whim, whimsey, freak, maggot, caprice, vagary, start and conundrum.

Both German Grille and French grillon are derived from Latin grillus, or gryllus, meaning cricket, grasshopper. In A Dictionarie of the French and English Tongues (1611), Randle Cotgrave wrote:

Grillon des champs [= of the fields]: a grasshopper; de cheminée [= of chimney]: a cricket.
Il a beaucoup de grillons en la tête [= He has a lot of crickets in the head]. He is in his dumps; his head is much troubled, full of crotchets [= whimsical fancies], or of proclamations.

French also had the phrase avoir des rats dans la tête, literally to have rats in the head, which referred to a changeable, whimsical person. According to John S. Farmer in Slang and its Analogues Past and Present (1890), this French phrase corresponds to the English to have rats in the upper storey. Farmer mentions many other French expressions; for example:
– avoir un asticot dans la noisette, literally to have a maggot in the hazelnut, corresponding to an English phrase a worm in the bud,
– avoir un cancrelat dans la boule, literally to have a cockroach in the ball,
– avoir un hanneton dans le réservoir, literally to have a cockchafer in the cistern.

Among the French expressions listed by Farmer, the only one still currently used is avoir une araignée au plafond, literally to have a spider at the ceiling (cf. to have bats in one’s belfry).

 

The Irish satirist, poet and Anglican cleric Jonathan Swift (1667-1745) evoked the notion of tiny creatures living in the brain in A Discourse Concerning the Mechanical Operation of the Spirit (1704):

It may not be amiss to add a few words upon the laudable practice of wearing quilted caps; which is not a matter of mere custom, humour, or fashion, as some would pretend, but an institution of great sagacity and use; these, when moistened with sweat, stop all perspiration, and, by reverberating the heat, prevent the spirit from evaporating any way, but at the mouth; even as a skilful house-wife, that covers her still with a wet clout, for the same reason, and finds the same effect. For, it is the opinion of choice virtuosi, that the brain is only a crowd of little animals, but with teeth and claws extremely sharp, and therefore cling together in the contexture we behold, like the picture of Hobbes’s leviathan, or like bees in perpendicular swarm upon a tree, or like a carrion corrupted into vermin, still preserving the shape and figure of the mother animal. That all invention is formed by the morsure of two or more of these animals, upon certain capillary nerves, which proceed from thence, whereof three branches spread into the tongue, and two into the right hand. They hold also, that these animals are of a constitution extremely cold; that their food is the air we attract, their excrement phlegm; and that what we vulgarly call rheums, and colds, and distillations, is nothing else but an epidemical looseness, to which that little commonwealth is very subject, from the climate it lies under. Farther, that nothing less than a violent heat, can disentangle these creatures from their hamated station of life, or give them vigour and humour, to imprint the marks of their little teeth. That, if the morsure be hexagonal, it produces Poetry; the circular gives Eloquence: if the bite hath been conical, the person, whose nerve is so affected, shall be disposed to write upon Politics; and so of the rest.