Green’s Dictionary of Slang

lap n.1

[euph.; but note SE lap, a fold of flesh]

[late 15C–17C] the vagina.

In derivatives

lapful (n.) [19C–1920s]

1. a husband; a lover.

2. an unborn child.

In compounds

lap-clap (n.) [SE clap, a blow] [17C–mid-18C]

1. sexual intercourse.

2. conception; thus get a lap-clap, to become pregnant.

lapland (n.)

1. [late 17C–19C] the vagina; thus Lapland witch, a prostitute.

2. [1920s+] the world of women.

lap-lover (n.)

[1970s+] one who enjoys cunnilingus.

SE in slang uses

In phrases

under the lap (adv.) (Aus.)

1. [late 19C+] confidentially; also as adj.

2. [20C+] orig. of betting, clandestinely; also as adj.