Green’s Dictionary of Slang

1. to laugh or shout loudly; thus yocky adj., hilarious [echoic; cf. yuk v.].

1938		H.M. Anderson Strip Tease 44: ‘Listen to ’em yock out there,’ says the comic after his bit ... ‘yock’ is a belly laugh.
1955		H. Kurtzman Inside Mad (2002) 35: That’s it kids! Really yock it up!
1961		J. Kirkwood There Must Be a Pony! 21: And what sense of humour! Not a great big yocky one, but more of a small, subtle, twinkling one.
1972		S.J. Perelman letter 14 Jan. in Crowther Don’t Tread on Me (1987) 275: The David Frost yocking it up ahead of the joke, the whole dismal syndrome.
2001		(con. 1964–8) J. Ellroy Cold Six Thousand 523: The crowd yocked. The crowd roared.
2023		(con. 1962) J. Ellroy Enchanters 28: ‘Zanuck is planning to reshoot [Cleopatra] with Lassie and Rin Tin Tin in the lead roles.’ I yocked.

2. to spit [SE hawk].

1998

K. Sampson Awaydays 84: I kick him in the side of the head and stamp on his ear and yock on him to let him know he’s shit.