screwball

The word 'screwball' is a compound formed from two common English nouns. Its literal sense emerged in early 20th-century baseball terminology, directly combining 'screw', implying a twisting motion, with 'ball', the projectile, to describe a pitch that moves with an unconventional spin. This sporting term, denoting erratic and unpredictable behavior, was then figuratively extended to describe a person whose ideas or actions are similarly unconventional and seemingly irrational. The logic of the word's evolution is clear: from a physical twisting action applied to an object, to the metaphorical application for describing human eccentricity.

Structure: screw (twist, fasten) + ball (sphere, projectile) 'screw' (Middle English, from Old French 'escroue', of Germanic origin; a cylindrical fastener with a helical ridge). 'ball' (Middle English, from Old Norse 'bǫllr'; a spherical object).