means A lineup is an arranged row of people or things—suspects displayed for identification, players named before a game, or acts scheduled to perform.

from A plain compound of "line" plus "up," born of the same logic that gives us "line up" as a verb: to arrange in a line. The noun form emerged in American English in the early 20th century, splitting its life between the sporting world (the roster set out before play) and the police station (suspects ranged against a height-marked wall for a witness's nervous eye). "Line" itself traces back through Old English and Latin "linea," a string or thread of flax—so every lineup is, at root, people strung along an invisible thread.