1. [late 16C+] to hit, to beat, to flog; also fig. use; thus whapper, woppern.
2. [mid-17C] to have sexual intercourse.
3. [mid-19C+] to overcome, to surpass, to defeat.
4. [1910s] (US) to shoot.
[1960s+] of a man, to have sexual intercourse; esp. in I could whop it up her/that, I would like to have sex with that woman.