screwball (n.)

"eccentric person," 1933, U.S. slang, earlier as a type of erratic baseball pitch (1928), from a still earlier name for a type of delivery in cricket (1866), from screw (n.) + ball (n.1). Screwball comedy is attested from 1937, in reference to the work of Carole Lombard.

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Definitions of screwball from WordNet
screwball (n.)
a whimsically eccentric person;
Synonyms: crackpot / crank / nut / nut case / fruitcake
screwball (n.)
a pitch with reverse spin that curves toward the side of the plate from which it was thrown;
screwball (adj.)
foolish; totally unsound;
a screwball proposal without a prayer of working
Synonyms: crazy / half-baked / softheaded