means A trap—often a noose or loop of wire—for catching small animals, or by extension anything that ensnares; also the wire strands stretched across a drum's underside that give it its sharp rattling buzz.

from From Old Norse 'snara,' a noose or snare, related to the verb 'snara,' to twist or wind—the trap named for the coiled cord that does the catching. The same twisting idea later wrapped itself around the drum: the 'snares' are wires snared tight across the head, so a snare drum is, quite literally, a drum caught in a loop of strings.