Green’s Dictionary of Slang

1. drunk, one has fallen there; thus drink under the table, to outdrink a fellow-drinker [popularized by George Washington ‘Chuck’ Connors, a New York character known as ‘the Bowery philosopher’].

1603		J.Dod Bright Star n.p.: [R]iotous seruants, that can rid of no worke, but meat and drinke, to carowse and drinke healths, and drinke one an other vnder the table.
1818		M.L. Weems Drunkard’s Looking Glass (1929) 60: The drunkard’s looking glass, reflecting a faithful likeness of the drunkard, in sundry very interesting attitudes, [...] as first, when he has only ‘a drop in his eye;’ second, when he is ‘half shaved;’ third, when he is getting ‘a little on the staggers or so;’ and fourth, and fifth, and so on, till he is ‘quite capsized;’ or ‘snug under the table with the dogs,’ and can ‘stick to the floor without holding on.’.
1849		Elgin Courier 30 Nov. 1/7: The fox-hunting parson [...] who saw with unmuddled brain his flock sink one by one under the table. ‘Drunk!’.
1855		Western Times 15 Sept. 6/5: A prostitute lying under the table drunk.
1871		Scotsman 10 Oct. 6/3: They indulge most freely in witty sayings [...] but these are always taken in good part [...] There is no falling under the table drunk.
1885		Bulletin (Sydney) 6 June 11/3: The title [of the new paper] is to be Table Talk. If the literary style of the prospectus may be taken as a sample of that of the paper, we would advise the promoters to lengthen the title to Under the Table Talk.
1889		Illus. London News 23 Feb. 19/3: Dean Swift, whose ‘Journal to Stella’ [...] describes Cabinet Ministers as falling under the table drunk.
1909		Justice 26 June 5: If you sit and play cards for high stakes [...] and drink wine until you roll under the table drunk, that’s good ‘form’.
1915		Daily Trib. (Bismarck, ND) 13 Apr. 4/5: The young lobster who [...] goes into the back doors of booze joints and tries to drink the whole bunch under the tables.
1937		P. Cheyney Dames Don’t Care (1960) 87: She could drink him under the table any day.
1942		C.R. Bond 12 Feb. in A Flying Tiger’s Diary (1984) 98: A few others tried to drink the RAF under the table.
1952		B. Appel Plunder (2005) 221: A few more and Tommy’d be under the table.
1967–8		Baker et al. CUSS 217: Under the table Drunk.
1976		P. O’Farrell Book of Irish Soldiers’ Jokes 19: For serving all the fellows that drink themselves under the tables.
1983		J. Ciardi A Second Browser’s Dict. 278: Drink (someone) under the table. To outlast a fellow sot in competitive drinking.

2. (also under the bed) clandestine, secret, corrupt; also as adv.

1935		A.J. Pollock Und. Speaks n.p.: Under the bed, told in confidence.
1938		F.D. Sharpe Sharpe of the Flying Squad 334: under the table: Something given as a bribe.
1952		Lait & Mortimer USA Confidential 92: Liquor licenses cost anywhere from $10,000 to $50,000 under the table.
1955		B. Appel Tough Guy [ebook] ‘This holdin’ out on me’s no good. This playin’ under the table’s n.g. twice over’ [ibid.] An under-the-table man, John Terry, shot down [after] one under-the-table deal too many.
1962		S. Longstreet Flesh Peddlers (1964) 80: This Henly, will he take a little under the table?
1972		Knapp Commission Report Dec. 156: [M]embers of the Hack Bureau of the Police Department, which regulates taxis and taxi drivers, charged drivers and owners under-the-table fees.
1977		D. Powis Signs of Crime 204: Table, under the Dishonestly or corruptly.
1983		J. Ciardi A Second Browser’s Dict. 278: Under the table 1. Covertly, as in money changing hands secretly, or in cheating at cards.
1990		(con. early 1950s) J. Ellroy L.A. Confidential 175: I know he’s bankrolled a lot of movies under the table.
2000		F.X. Toole Rope Burns 25: He also picks up a couple of hundred under the table each time he sells a boy out.
2010		(con. 1973) C. Stella Johnny Porno 101: You talking legit or under the table.