romp v.

c. 1300, raumpen, "to climb; to stand on the hind legs" (of animals), from Old French ramper "to climb, scale, mount" (12c., in Modern French "to creep, crawl"), a word of uncertain origin, perhaps from Frankish *rampon "to contract oneself" (compare Old High German rimpfan "to wrinkle," Old English hrimpan "to fold, wrinkle"), via notion of the bodily contraction involved in climbing [Klein], from Proto-Germanic *hrimp- "to contract oneself."

Hence, of a person or a devil," "attack, behave menacingly, as a lion or wolf would" (late 14c.). Related: Ramped; ramping.

"coarse, frolicsome girl or woman," mid-15c., rampe, "a virago, shrew," perhaps from early senses of ramp (v.) via the notion of "rear up on the hind legs to attack," hence, of persons, "to attack like a rampant animal." Also compare ramp (n.1). Johnson's Dictionary (1755) has romp: "a rude, awkward, boisterous, untaught girl."

1842, "one who romps," agent noun from romp (v.). Rompers "small children's overalls" is attested by 1909, with ending perhaps on the model of trousers.