play (v.)
Old English plegan, plegian "move rapidly, occupy or busy oneself, exercise; frolic; make sport of, mock; perform music," from West Germanic *plegan "occupy oneself about" (cognates: Old Saxon plegan "vouch for, take charge of," Old Frisian plega "tend to," Middle Dutch pleyen "to rejoice, be glad," German pflegen "take care of, cultivate"), from PIE root *dlegh- "to engage oneself," forming words in Celtic, Germanic, Slavic, and possibly Latin.

Meaning "to take part in a game" is from c.1200. Opposed to work (v.) since late 14c. Related: Played; playing. To play up "emphasize" is from 1909; to play down "minimize" is from 1930; to play along "cooperate" is from 1929. To play with oneself "masturbate" is from 1896; play for keeps is from 1861, originally of marbles or other children's games with tokens. To play second fiddle in the figurative sense is from 1809 ("Gil Blas"). To play into the hands (of someone) is from 1705. To play the _______ card is attested from 1886; to play fair is from mid-15c. To play (something) safe is from 1911; to play favorites is attested from 1902. For play the field see field (n.).
play (n.)
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.)). Meaning "dramatic performance" is attested by early 14c., perhaps late Old English. Meaning "free or unimpeded movement" of mechanisms, etc., is from c.1200. By early Middle English it could mean variously, "a game, a martial sport, activity of children, joke or jesting, revelry, sexual indulgence." 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."