OK - let's cut to the chase!

Partridge in his Dictionary of Historical Slang has

twang To coït with (a woman): cant : C. 17-18
So a word from the criminal underworld. He makes no attempt at derivation.


He also has
twang(e)y. A tailor: North Country: ca. 1780-1850.
This tailor sense was mentioned earlier in the thread.

Regards