mee mee mee It's from a nursery rhyme. It is "the lasst little piggy."
Eric Partridge records this in his A Dictionary of Slang, 1937, as "Wee-wee, a urination; esp. do a wee-wee" and considers it to be late 19th century.
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yes
Oski Wee Wee! Oski Waa Waa! Holy Makinaw! Tigers! Eat'em Raw! Hamilton Tiger Cats Football cheer Won't tell you what an "Oski" is nor why he is going wee wee and waa waa.