The Irish-English phrase to beat (or to bate, to bang) Banagher means to surpass everything.
The origin of the phrase to beat (or to bate, to bang) Banagher is unclear.
The most convincing explanation that I have found is as follows, from Remarks on the Irish Dialect of the English Language, by the Rev. Canon Hume, read on Thursday 7th February 1878, published in Transactions of the Historic Society of Lancashire and Cheshire (Liverpool: Adam Holden, 1878)—Banagher is a town on the banks of the River Shannon, in County Offaly (formerly known as King’s County), in the province of Leinster, Ireland:
There is a certain class of words, nouns and adjectives, derived from geographical names. In general they indicate the productions of those places respectively; but an investigation of the whole subject shows that they have a much wider range. […]
Blarney, language of persuasive flattery. It is said that there is a stone in the castle wall of Blarney, near Cork, the kissing of which enables the operator ever after to exercise this faculty.
We also say, “that bangs Banagher,” from a strong military fort at that place, on the banks of the Shannon; or of a person who cannot be outwitted “he could keep Omagh,” i.e., serve as Governor to that important county prison. A remove to some very remote place is said to be “to Dingle ty-cootch,” viz., to Dingle or “Dingle-i-couch” in Kerry, the most Western town in Ireland.
The following two explanations seem to me less convincing:
1-: From A Classical Dictionary of the Vulgar Tongue (London: S. Hooper, 1785), by the English antiquary and lexicographer Francis Grose (1731-1791):
Banaghan, he beats Banaghan, an Irish saying of one who tells wonderful stories, perhaps Banaghan was a minstrel famous for dealing in the marvellous.
2-: From Dictionary of Phrase and Fable, giving the Derivation, Source, or Origin of Common Phrases, Allusions, and Words that have a Tale to Tell (London: Cassell, Petter, and Galpin, ), by the English educationist and lexicographer Ebenezer Cobham Brewer (1810-1897):
That beats Ban’agher. Wonderfully inconsistent and absurd—exceedingly ridiculous. Bauagher [sic] is a town in Ireland, on the Shannon, in the King’s County. It formerly sent two members to parliament, and was, of course, a famous pocket borough. When a member spoke of a family borough where every voter was a man employed by the lord, it was not unusual to reply, “Well, that beats Banagher.”
The earliest occurrences of the phrase to beat (or to bate, to bang) Banagher that I have found are as follows, in chronological order:
1-: From The British Press and the Irish People, published in The Dublin Evening Post (Dublin, County Dublin, Ireland) of Thursday 13th September 1821—this newspaper commented on a quotation from The Edinburgh Star (Edinburgh, Midlothian, Scotland):
“It would appear that his Majesty went to Ireland, not more with an intent to harmonize that Country within itself, than in order to disunite it from England.”
Good!—mighty good!—most excellent good! The sagacity of your Scotchmen is really astonishing! The murder is out; we have now the meaning of your necessary separation of old coherences. It means, that we meant, that the King came to Ireland for the purpose of disuniting from England—of cutting the painter, as Walter Cox said in language more figurative and striking. This positively beats Banagher. Talk of the man who maintained that the stars were made of ice, because they shone brightly in frosty weather; he was as opaque as a lump of lead compared to this bright Star of Edinburgh.
2-: From The King and the Scotch, published in The Dublin Evening Post (Dublin, County Dublin, Ireland) of Thursday 29th August 1822—this newspaper ridiculed the account, by “a Scotch Newspaper”, of the King’s visit to Scotland:
We proceed with our quotations:
“At Holyrood House his Majesty said that ‘he had been often told the Scotch were proud; and well might they be, they seem to me to be a Nation of Gentlemen!’”
A Nation of Gentlemen! We wish that the Ladies of these Gentlemen would spare our poor Southern Dandies from a ducking—or worse. But positively this bangs Banagher. The King, every one knows, never said any thing so absurd, as that every itchy hostler or thieving gaberlunzieman in Scotland was a Gentleman.
3-: From Dramatic Travels. The Diligence from Paris to Lyons, published in The New Monthly Magazine and Literary Journal. Vol. VII. Original Papers (London: Printed for Henry Colburn and Co., 1823):
Give me a Diligence, that pleasant misnomer, that with sixteen, eighteen, nay, twenty passengers, stowed in three cabins, and a parachute-looking affair called a Cabriolet, at top, together with I know not how many tons weight of baggage, rolls along the pavé at the rate of two-miles-and-a-half per hour, stoppages non-included. “Didst ever see a Diligence?”—Wert thou ever, then, at Chelsea or Battle-bridge, at Greenwich or Brook-Green fair?—Saw’st thou the elephant’s vehicle and habitation, or that of the lions?—“Walk in, gentlemen!”—You may remember these. Such is a Diligence! And lumbering vehicles as they are, enough indeed to drown any John Bull in a flood of spleen, yet, let me tell you, the yard of the Messageries Royales beats out and out your White Horse Cellar, or your Swan with Two Necks. I don’t talk of Portsmouth, or Liverpool, or voyages in the sea-way, for “that beats Banagher,” as we Irishmen say.
4-: From Noctes Ambrosianæ. No. XIII, published in Blackwood’s Edinburgh Magazine (Edinburgh, Midlothian, Scotland) of March 1824:
ODoherty. Upon the whole it is not to be denied, that the divan have not half the spunk of their rival who rules in the west of the Empire of Cockaigne.
North. Joannes de Moravia? Have you seen him, ODoherty, in your travels?
ODoherty. Of course—of course—a most excellent fellow that said bibliopole is.
North. That I know. How does he carry on the war?
ODoherty. In the old style. Morier and his people are mad with you for your blackguard review of Hajji Baba.
North. My blackguard review, Mr Adjutant—it was you who wrote it.
ODoherty. I—Well, that beats Banagher.
Tickler. No matter who wrote it—it was a very fair quiz—better than anything in the novel—though really I must say that I consider Hajji rather an amusing book after all.
5-: From Mark Connor’s Wooing and Wedding, one of the Sketches of Irish Character, by the Irish author Mrs. S. C. Hall (Anna Maria Hall, née Fielding – 1800-1881), published in The Morning Journal (London, England) of Tuesday 4th August 1829—reprinted from The Spirit and Manners of the Age; A Christian and Literary Miscellany (London, England):
“Do you remember the last lot of pigs you sold me? […] Well, perhaps you recollect one with a black head—a long-bodied animal—strange made about the shoulders.”
“[…] I let you have her, a dead bargain.”
“Bargain, indeed! she would eat nothing we would give her, and knowing she was Irish, Helen picked the potatoes, mealy ones, and—”
Here Mark cast a look of indignation at his host, and exclaimed—
“Well, that bates bannaher [sic]; Miss Helen, who’s more like an angel than a woman, pick potatoes for an unmannerly sort of a pig; a Connaught pig, too, that could have no sort of manners!”