"to make a gentle ringing sound," 1382, possibly a frequentative form of tinken "to ring, jingle," perhaps of imitative origin. Meaning "to urinate" is recorded from 1960, from childish talk.
in. to urinate. (Mostly juvenile use. Usually objectionable.) : Jimmy, be sure and tinkle before we leave.
n. urine. (Essentially juvenile. Usually objectionable.) : There's tinkle on the bathroom floor.
Dictionary of American Slang and Colloquial Expressions by Richard A. Spears.Fourth Edition. Copyright 2007. Published by McGraw Hill.
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