1911 Encyclopædia Britannica/Play
PLAY, a word of which the primary meaning is that of free or active movement or exercise. The O. Eng. plegan or plegian, from which comes the substantive plega, play, is apparently cognate with Ger. pflegen, to take care or charge of, and Pflege, care, and the connexion in sense is to be found in the primary meaning, that of exercise or active movement. In its primary meaning “play” is used of the rapid changing movement of light and colour, and also figuratively of thought or fancy, and specifically of the free movement of parts of a mechanism on each other, of a joint or limb, &c. To play a musical instrument is to move the fingers upon it, and until the 18th century the verb was intransitive, and “ on ” or “ upon ” was always used with the name of the instrument. The very general use of the word for sport, game or amusement, is an early and easy development from the meaning of active movement or exercise as a recreation after work; that of a dramatic performance (see Drama) is very early; the New English Dictionary quotes from King Alfred's Orosius (c. 893).
The primitive play instinct or play impulse in man has been much discussed in recent years by psychologists in connexion with child study (see Child), and with the expression of the emotions (see J. Sully, On Laughter, 1902, &c; also Aesthetics). See generally Carl Groos, The Play of Animals (1898) and The Play of Man (1901); and Baldwin's Dict. of Philosophy, s.v.