Green’s Dictionary of Slang

oxter n.

(Irish/Scot.) an armpit.

c.1550		A. Scott Poems (1821) 41: In oxsteris cloiss, we kiss, and cossis hairtis, Brynt in desyre of amouris play and sport.
c.1580		A. Montgomerie Invectiues Capitane Allexander Montgomeree and Pollvart in Parkinson (Poems) (2000) II line 259: Sum in their oxteris it cleikis Lyk a bagpype.
1674		J. Ray Eng. Words Not Generally Used 23: An Oxter, an Armpit .
1724		A. Ramsay Tea-table Misc. (1733) II 178: She round about seeks Robin out, To slap it in his oxter. [Ibid.] 454: Oxter, arm-pit.
1768		A. Ross Helenore in Wattie Scot. Works (1938) 87: Her in her oxter hard an’ fast she grips.
1786		Young Coalman’s Courtship 5: You may tak her head in your oxter, like a creesh pig, dab nebs wi’ her now an’ than.
1823		Proceedings of Jockey and Maggy 22: The constable [...] catched John at his breakfast, hauls him awa, an at ilka oxter, like two butcher dogs, hingin at a bull’s beard.
1830		W. Carleton ‘The Three Tasks’ Traits and Stories of the Irish Peasantry I 51: Under my oxther! you swindling rascal.
1841		‘Bryan O’Lynn’ Dublin Comic Songster 18: Bryan O’Lynn was hard up for a coat, / He borrowed a skin of a neighbouring goat / With the horns sticking out from his oxters.
1879		C.J. Kickham Knocknagow 216: If poetry as well as music could be squeezed out of an Irish bagpipes, I’d say that ballad came out of that bag under his oxter.
1902		W.H. Ogilvie ‘Scotch Night‘ in Bulletin Reciter n.p.: You’re taken by the oxter and you’re couped into a chair .
1904		G.B. Shaw John Bull’s Other Island II ii: You can take the sammin under your oxther.
1916		R. Service ‘The Whistle of Sandy McGraw’ Rhymes of a Red Cross Man 153: The big stuff wis gorin’ and roarin’ around, / And I seemed tae be under the oxter o’ hell.
1922		Joyce Ulysses 308: And begob there he was passing the door with his books under his oxter.
1932		M. Marshall Travels of Tramp-Royal 45: He had [...] a badge on ae arm, twa-three meal pokes under his oxter.
1940		‘Flann O’Brien’ Third Policeman (1974) 161: You could have ten acres of land with strawberry jam spread on it to the height of your two oxters.
1952		B. MacMahon Children of the Rainbow 98: Christmans Eve it is an’ Molly Font is comin’ up Cloone with an elephant of a goose trapped in her oxter.
1969		P. Boyle All Looks Yellow to the Jaundiced Eye 79: Let you sink yourself to the oxters in a welter of delusion.
1979		J. Morrow Confessions of Proinsias O’Toole 58: She actually took hold of poor Steffers under the oxters and forced her.
1986		P. O’Farrell Tell me, Sean O’Farrell 38: The schoolhouse was very old and couldn’t be heated by the sods of turf that the pupils brought each day, tied to schoolbags or under their oxters.
1995		A. Higgins Donkey’s Years 90: Both hands were under his oxters.
1996		(con. 1970) G. Moxley Danti-Dan in McGuinness Dazzling Dark (1996) I ix: I don’t know where my skirt was, around my oxters I suppose.
2001		G. Coughlan Everyday Eng. and Sl. 🌐 Oxters (n): armpits.
2005		R. O’Donnell Doll Tower 15: Any of you laddies let me down wi yer oxter and foot hygiene, I’ll be sticking you on the fucking crap patrol wi a toothbrush and a bar o carbolic.
2015		L. McInerney Glorious Heresies 81: Up to me oxters in punishment I was, for doing feck all.
2023		Twitter 15 May 🌐 John Lone shaving Linda Fiorentino's oxters in The Moderns.

In derivatives

oxterful (n.)

as much as one can carry beneath an armpit.

1818

J. Hogg Wool-Gatherer 126: Gang after your braw gallant, wi’ your oxterfu’ ket.