Green’s Dictionary of Slang

armpit n.

[the link of the SE armpit with dirt and smell]

1. (orig. US) the least appetizing, poorest, most run-down and poss. dangerous area of a city or town; often as armpit of the nation/universe; also in phr. rough as a docker’s armpit.

[US] in Current Sl. IV:3–4 (1970) 12: Armpit of the nation, n. Las Cruces (New Mexico).
[Aus]Tracks (Aus.) Dec. 3: If some smart-arse asks you what it’s like to live in the arsehole of the country, ask them how the armpit is going [Moore 1993].
[UK]P. Theroux London Embassy 40: It was a John Baldwick, living in some armpit in east London.
[US](con. 1968) Bunch & Cole Reckoning for Kings (1989) 319: What a fucking armpit this is.
[UK](con. 1990s) N. ‘Razor’ Smith A Few Kind Words and a Loaded Gun 359: Stockwell Park Estate looked as rough as a docker’s armpit.

2. (orig. US) used similarly of a place, e.g. a nightclub or café.

[UK]F. Norman Guntz 86: She’s a stripper in this way out filthy little armpit of a night club.
[US]K. Huff A Steady Rain I i: I don’t want you going back to that armpit of a bachelor pad and sticking it to a bottle of Schnapps tonight.

3. (US campus) an unpleasant individual.

[US]Baker et al. CUSS 72: Armpit An obnoxious person.
[US] in Woodward & Bernstein The Final Days 231: ‘The armpit of humanity,’ he called Nixon.

In phrases

put someone up to their armpits (v.)

(UK Und.) to cheat an accomplice out of his share of the proceeds.

[UK]H. Brandon Dict. of the Flash or Cant Lang. 167/2: To put a fellow up to his arm-pits – to cheat a companion out of his share of the plunder.

SE in slang uses

In phrases

up to one’s armpits (also up to one’s diddies,’s nipples,’s tits, over one’s tits) [var. on up to the elbows under elbow n.1 ]

(orig. US) consumed by, overwhelmed by.

N.Z. Parliamentary Debates 925: I hope my friend, when he is up to his armpits in mud, will remember that the vestibule is a work of art.
[US]Hecht & Fowler Great Magoo 127: sam: Dough? weber: Up to his nipples.
[US]Newsweek LXXXI 333: A paunchy local Leo, round face glistening with sweat, had been up to his armpits in the free lunch.
E. Lustbader Ninja 158: Christ, she was up to her armpits in shit.
[US]S. King It (1987) 37: He was up to his tits in bills and there was no way he could see out of the red ink.
F. Weldon Growing Rich 215: See how Angela’s sandwich business went if she was up to her armpits in kids.
[Ire](con. 1945) S. McAughtry Touch and Go 82: Annie is up to her diddies in debt.
[Aus]P. Temple Black Tide (2012) [ebook] Bitch wanted Frank done. In it over her tits.
Herald (Scotland) 27 Jul. [Internet] [He] will reveal evidence that shows Baird, originally from Helensburgh, was ‘up to his armpits’ in top secret work for the government during the war years.
work under the armpits (v.) [SE work/work v. (4); ? above the armpits is the neck from which one can be hanged, so below this fig. line one is ‘safe’]

(UK Und.) to confine one’s criminality to such activities that would be classed as petty larceny, bringing a maximum sentence of seven years transportation, rather than hanging; thus work above the armpits v., to commit crimes that could lead to one’s execution.

[UK]Vaux Vocab. of the Flash Lang. in McLachlan (1964) 225: arm-pits: To work under the arm-pits, is to practise only such kinds of depredation, as will amount, upon conviction, to what the law terms single, or petty larceny; the extent of punishment for which is transportation for seven years. By following this system, a thief avoids the halter, which certainly is applied above the arm-pits.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.
[UK]Metropolitan Mag. 14 330: He’s a poor crawling wretch, who works under the armpits, to be banded, and hour’d up in a swimmer all his best days, and then to be tatted.