Green’s Dictionary of Slang

cap n.1

[abbr.; Ware cites some UK use but cap’n n. is more common]

(orig. mainly US) captain; often as a term of address.

[US]Spirit of the Times (N.Y.) 17 Oct. 391/3: The old cap. wanted to kill one o’ them varmints [DA].
[UK]M. Reid Scalp-Hunters II 137: Why, Cap., yur tumble has surely dumbfoundered ye.
[US]G.W. Whitman in Civil War Letters 12 April 50: Cap has bread made in the Citty.
[US]J. O’Connor Wanderings of a Vagabond 35: ‘Show your papers, Cap,’ said Giles, seeing him hesitate.
[UK]Sheffield Indep. 17 Jan. 9/1: ‘You see, Cap,’ added Rick, giving a reason for his request.
[US]J. Hay Bread-Winners (1884) 140: ‘Hold on, Cap,’ he said.
[US]J. Hawthorne Confessions of Convict 35: One evening Cap. sprang his massy lever.
[US]H. Garland Eagle’s Heart 80: Don’t you worry, cap, I’m not drinkin’ liquor of any colour.
[US]J. Flynt World of Graft 91: The Cap says you want me to chew the rag about municipal corruption.
[NZ]Marlborough Exp. (N.Z.) 3 June 3/2: They rest called Fred ‘cap’ when they wanted to touch him up till pay-day.
[US]F. Packard Adventures of Jimmie Dale (1918) I iv: The Cap’ll be along in a minute.
[US]‘Digit’ Confessions of a Twentieth Century Hobo 41: As far as I’m concerned, cap., you’re about seven years too late.
[US]J. Conroy World to Win 57: ‘Not so good, Cap,’ the cook answered jovially.
[US]R. Chandler Lady in the Lake (1952) 167: Hi, Cap, I got a little murder down here cluttering up the front-room.
[US]C. Himes ‘A Penny for Your Thoughts’ in Coll. Stories (1990) 56: His name was Frank Hacket but people in Red River, Texas, where he lived, called him Cap Coty.
[US]W.R. Burnett Little Men, Big World 191: It’ll make you look pretty big right now won’t it? Knocking over all these gambling joints? Go to it, Cap.
[US]M. Braly On the Yard (2002) 213: ‘He’s through. Tell him I said so.’ ‘I’ll do that, Cap.’.
[US]Fantastic Four Annual 24: Cap! Do you see what I see?
[US]L. Heinemann Paco’s Story (1987) 22: The cap got all pissed off and had another shit fit.
B.Y. Gifford Night People 130: Enjoy you self, Cap.