OKAY. Since no Francophone or Francophile responded, I will. I refer to --- https://www.imagefap.com/photo/614938151/ --- . POON is an abbreviation from POONTANG as in the song ``Wang Dang Sweet Poontang`` (1977) by Ted Nugent about sex with a groupie. I assume POONTANG = CUNT is from French PUTAIN = WHORE. Americans will more likely recognize Spanish PUTA = WHORE. There may have even been an obsolete dialectic use as American hillbillies have some usages from Elizabethan or even Old English. PUT and PUTAIN are obviously from Latin PUTEUS = WELL HOLE. In the Classical Latin porn novel Satyricon by Petronius one character cheated a prostitute. She didn`t need a pimp to beat him up. Prostitution was completely legal so she took him to court. His defense was he leased a property and when he came on it there was a huge well hole so wide and deep a man could fall in it and die. So he improved the property by filling the huge hole and he reckoned that value was equal to the lease. Yes, countered the plaintiff`s attorney, but you removed the improvement. Anyway, Petronius comes very close to turning PUTEUS = WELL HOLE into PUTEA which would mean FEMALE WELL HOLE hence CUNT hence SLUT hence WHORE. I don`t think Petronius innovated this usage. My guess is that PUTEA was an unrecorded piece of Vulgar Latin which surfaced later in the Romance languages.
