cap, v.² — Green’s Dictionary of Slang

cap v.²

also kap

[Lat. capias, you may take – a term used in a variety of legal writs, e.g. capias ad respondendum, to enforce attendance at court, and capias ad satisfaciendum, after judgement, to imprison the defendant until the plaintiff’s claim is satisfied]

(UK Und.) to swear an oath.

c.1698		B.E. Dict. Canting Crew.
1719		A. Smith Lives of Most Notorious Highway-men, etc. (1926) 203: Cap, to swear. I’ll cap downright, i.e., I’ll swear home.
1725		New Canting Dict.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict.
c.1750–1882		B.M. Carew Life and Adventures.
1753		J. Poulter Discoveries (1774) 43: He kaps quare; he swears false.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1809		G. Andrewes Dict. Sl. and Cant.
1811		Lex. Balatronicum.
1821		Flash Dict.
c.1850		Duncombe New and Improved Flash Dict.

cap v.2

cap v.²