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" (cf. 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.).