Trap
Old English træppe (in coltetræppe ‘Christ's thorn’); related to Middle Dutch trappe and medieval Latin trappa, of uncertain origin. The verb dates from late Middle English.
wiktionary
From Middle English trappe, from Old English træppe, treppe(“trap, snare”) (also in betræppan(“to trap”)) from Proto-Germanic *trap-, from Proto-Indo-European *dremb-(“to run”).
Akin to Old High German trappa, trapa(“trap, snare”), Middle Dutch trappe(“trap, snare”), Middle Low German treppe(“step, stair”) (German Treppe "step, stair"), Old English treppan(“to step, tread”) and possibly Albanian trap(“raft, channel, path”). Connection to "step" is "that upon which one steps". French trappe and Spanish trampa are ultimately borrowings from Germanic.
Borrowed from Swedish trapp(“step, stair, stairway”), from Middle Low German trappe(“stair, step”).
Akin to Middle English trappe(“trappings, gear”), and perhaps from Old Northern French trape, a byform of Old French drap, a word of the same origin as English drab(“a kind of cloth”).
Shortening.
etymonline
trap (n.)
"contrivance for catching unawares," late Old English træppe, treppe "snare, trap," from Proto-Germanic *trep- (source also of Middle Dutch trappe "trap, snare"), related to Germanic words for "stair, step, tread" (Middle Dutch, Middle Low German trappe, treppe, German Treppe "step, stair," English tread (v.)).
This is probably literally "that on or into which one steps," from PIE *dreb-, an extended form of a root *der- (1), base of words meaning "to run, walk, step." The English word is probably akin to Old French trape, Spanish trampa "trap, pit, snare," but the exact relationship is uncertain.
The sense of "deceitful practice, device or contrivance to betray one" is recorded from c. 1400. The meaning "U-shaped section of a drain pipe" is from 1833. Slang meaning "mouth" is from 1776. Speed trap is by 1908. Trap-door "door in a floor or ceiling" (often hidden and leading to a passageway or secret place) is attested from late 14c. (trappe-dore).
trap (v.)
late 14c., "ensnare (an animal), catch in a trap; encircle; capture," from trap (n.) or from Old English betræppan. Figurative use is slightly earlier (late 14c.). Related: Trapped; trapping.
