More precisely - British slang for a resident of Cardiff and it's environs (from the River Taff which runs through it). Derived from the days when Cardiff was the busiest sea port in the world (due to coal exports) - "Taff" or "Taffy" was a reference to the workers on the docks.

A jack off buddy (from 'cum' /'come', meaning 'semen', and 'companion'); a friend that you get together with for sessions of solo or mutual masturbation
Variant of: cumpanion (from 'companion' & 'cum'); jack off buddy & wank bud & JO buddy
Similar to: fuck buddy

Sexual act of stimulating the female genitals with the tongue.

Word was coined from a Ghanaian slang, Tafrisky, which means “cunnilingus”.

Where back in the day it may of meant Welshmen originating from around the Cardiff area or River Taff area, now usually mean someone from the whole South Wales area.
A commen misconception though is that all people from Wales are called TAFF..wrong people from North Wales are commenly known as Gogs because North in Welsh is Goggledd.

Saying all that there is also the rumour that TAFF stands for....Thick As Fucking Fuck

English slang name for someone from Wales.

Have a pull, a wank, a flog, a taff.

a Taff is someone from Wales. See Paddy