George Carlin referred to the Seven Words You Can Never Say On Television as "Anglo-Saxon" (i.e. Old English). Piss, however, is not Old English at all; it's a straight borrowing from French. The agent ending -er in cocksucker and motherfucker is also a borrowing from French -ier, though some words ending in -arius, the Latin ancestor of -ier, entered Old English and now show -er as well.
Fuck and cunt are certainly not French, but don't look like Old English either, for phonological reasons; they are probably borrowings from other Germanic languages. There may be a remote connection to Latin cunnus, as in Latin and Englishcunnilingus.
The remaining two words (shit and tits) as well as the roots cock, suck, and mother, would be quite as clear to Anglo-Saxons (allowing for changes in pronunciation) as to us.