piss:  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  started life as a euphemism for piss. => pee
late 13c., from Old French pissier "urinate" (12c.), from Vulgar Latin *pissiare, of imitative origin. To piss away (money, etc.) is from 1948. Related: Pissed; pissing. Pissing while (1550s) once meant "a short time."
He shall not piss my money against the wall; he shall not have my money to spend in liquor. [Grose, "Classical Dictionary of the Vulgar Tongue," 3rd edition, 1796]
late 14c., from piss (v.). As a pure intensifier (piss-poor, piss-ugly, etc.) it dates from World War II. Piss and vinegar first attested 1942. Piss-prophet "one who diagnosed diseases by inspection of urine" is attested from 1620s. Piss proud "erect upon awakening" is attested from 1796.