piss: [13] Piss probably originated in imitation of the sound of urinating. It has been traced back to a hypothetical Vulgar Latin *pisāre, which passed into English via Old French pisser. It has become widely distributed throughout the other European languages (Italian pisciare, for instance, German and Dutch pissen, and Welsh piso). Pee [18] started life as a euphemism for piss. => pee[piss etymology, piss origin, 英语词源]