Green’s Dictionary of Slang

1. the foreskin.

1889

1889

C. Devereux Venus in India [no text] [Simes:DLSS].

2. the glans penis.

1946

195019601970198019902000

2001

1946		in Randolph & Legman Unprintable’ Ozark Folksongs and Folklore [npo text] [Simes:DLSS].
1993		Gay Letters (NY) Nov. 80/2: I just suck the cap, moving it in and out of my lips quickly [Simes:DLSS].
2001		Tender Chickens (NY) Aug. 14/1: [W]idening my o-ringing mouth to accommodate the swelling base of the cap [Simes:DLSS].

3. (US) fellatio.

1974

1974

in Lighter HDAS.

4. see bonnet n.¹