From Etymonline
Rampage (v)
“rage or storm about,” 1715, in Scottish, probably from Middle English verb ramp “rave, rush wildly about” (c. 1300), especially of beasts rearing on their hind legs, as if climbing, from Old French ramper (see ramp (v.), also see rampant). Related: Rampaged; rampaging.
A huge untamed beast on its hind legs, an unnatural stance, reaching beyond what Nature has given it, stretching upwards to reach out wildly and destructively in its unhappiness.