type of game bird, 1530s, grows (plural, used collectively), of unknown origin, possibly from Latin or Welsh.
"complain," 1885 (implied in grousergroucer, from Old French groucier "to murmur, grumble," of imitative origin (cf. Greek gru "a grunt," gruzein "to grumble"). Related: Groused; grousing. As a noun from 1918, from the verb.
To complain; bitch: No grousing, no foot-dragging, both signs of a solid pro (1887+ British armed forces)