1590s, back-formation from urination or else from Medieval Latin urinatus, past participle of urinare, from urina (see urine). Related: Urinated; urinating.
Synonyms: make / piddle / puddle / micturate / piss / pee / pee-pee / make water / relieve oneself / take a leak / spend a penny / wee / wee-wee / pass water