the.com/deadfall

a trap that kills with the weight of the world, no batteries required.

means A deadfall is a heavy weight rigged to fall and crush prey when triggered, or simply a pile of fallen, dead timber in a forest.

from A plain compound of "dead" and "fall," both from Old English roots — "dead" (Old English dēad) and "fall" (from feallan, to drop). The word names exactly what it does: something dead, or something that falls deadly. The trapping sense and the "tangle of fallen trees" sense both grew naturally from this literal pairing, with the trap meaning especially common in North American frontier and hunting talk.

how it works: heavy object propped to crush whatever trips it
forest meaning: tangled mass of fallen, rotting timber
figure-four: three sticks balance the entire deadly load
survival staple: taught in bushcraft for catching small game
old word: used since the 1600s for both senses

for instance

deadfall trap — ancient hunting device using gravity-triggered logs, documented in indigenous practices across north america and asia

deadfall creek — stream in british columbia, canada, named for accumulated fallen timber

deadfall lake — alpine lake in the cascade range, washington state, surrounded by stands of fallen trees