"clever person," 1914, probably a special use of whiz "something remarkable" (1908), an extended sense of whizz; or perhaps a shortened form of wizard. Noun phrase whiz kid is from 1930s, a take-off on a radio show's quiz kid.
A very successful performer; an outstanding expert; humdinger: the town's most promising high school football whiz/ a whiz at exterior (as opposed to psychological) characterization
[1914+; perhaps a shortened form of wizard]
: I just came down for a whizz (1971+)verb
To urinate; piss: exactly twenty-five minutes after whizzing in his pants for the last time/ I gotta whiz. Will you just cover me at the register for a minute? (1929+)
[perhaps echoic; perhaps related to late 1800s British hold your whiz, ''be quiet, shut up,'' similar to hold your water]