rampage 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.

c. 1300, raumpaunt, "standing on the hind legs" (as a heraldic lion often does), thus, also, "fierce, ravenous" (late 14c.), from Old French rampant, rampans, present participle of ramper "to climb, scale, mount" (see ramp (v.)). Sense of "growing without check" (in running rampant), is recorded by 1610s, probably is via the notion of "fierce disposition" or else preserves the older French sense. Related: Rampantly.