Green’s Dictionary of Slang

1. a sleep [= kip n.¹ (3)].

1998

R. Puxley Fresh Rabbit.

2. a nipple.

2002

Fabian & Byrne Out of Time (ms.) 101: When he tried to tweak her walnut whips she slapped him away, laughing, and told him not to spoil things.

3. a vasectomy [= SE snip].

1999

Roger’s Profanisaurus in Viz 98 Oct. 30: walnut whip rhym. slang. A minor operation which removes the cream, but leaves the nuts intact. The snip.