Green’s Dictionary of Slang

waps n.

also wap-waps
[SE wap, to move, to shake]

the female breasts.

[UK]Roger’s Profanisaurus in Viz 87 Dec. n.p.: wap-waps n. Breasts. Also dedoo-wap-waps.
[Aus]Sydney Morn. Herald 3 July 🌐 Norgren congratulated her on her waps – British slang for breasts – at an office Christmas lunch.