German 'pflegen' (to tend, cultivate) is 'play's' continental cousin — the root was vigorous engagement, not fun.
To engage in activity for enjoyment and recreation; to take part in a game or sport; to perform on a musical instrument.
From Old English 'plegian' (also 'plegan') meaning 'to exercise, move rapidly, make sport of,' from Proto-Germanic *plegōną or *plegijaną. The original sense involved rapid physical movement and exercise rather than recreation. Cognate forms in continental Germanic meant 'to vouch for, pledge, risk' — a meaning preserved in Middle Dutch 'plegen' (to be accustomed to, to take care of). The connection between 'rapid movement,' 'risk-taking,' and 'play' likely lay in the context of competitive games and physical contests. Key roots: *plegōną (Proto-Germanic: "to move quickly
German 'pflegen' (to tend, care for, cultivate) is the cognate of English 'play' — meaning the same Proto-Germanic root that produced English's word for recreation produced German's word for dutiful care, a dramatic example of how the same ancestral word can evolve in opposite emotional directions.