pee (v.) Look up pee at Dictionary.com
1788, "to spray with urine," euphemistic abbreviation of piss. Meaning "to urinate" is from 1879. Related: Peed; peeing. Noun meaning "act of urination" is attested from 1902; as "urine" from 1961. Reduplicated form pee-pee is attested from 1923.