Old English plega (West Saxon), plæga (Anglian) "quick motion; recreation, exercise, any brisk activity" (the latter sense preserved in swordplay, etc.), from or related to Old English plegan (see play (v.)). By early Middle English it could mean variously, "a game, a martial sport, activity of children, joke or jesting, revelry, sexual indulgence."
Meaning "dramatic performance" is attested by early 14c., perhaps late Old English. Meaning "free or unimpeded movement" of mechanisms, etc., is from c. 1200. Sporting sense "the playing of a game" first attested mid-15c.; sense of "specific maneuver or attempt" is from 1868. To be in play (of a hit ball, etc.) is from 1788. Play-by-play is attested from 1927. Play on words is from 1798. Play-money is attested from 1705 as "money won in gambling," by 1920 as "pretend money."