threshold (n.) Look up threshold at Dictionary.com
Old English þrescold, þærscwold, þerxold, etc., "door-sill, point of entering," probably literally "something to tread upon," with first element related to Old English þrescan (see thresh), with its original sense of "tread, trample." Second element of unknown origin and much transformed in all the Germanic languages, suggesting its literal sense was lost even in ancient times. In English it probably has been altered to conform to hold, but the oft-repeated story that the threshold was a barrier placed at the doorway to hold the chaff flooring in the room is mere folk etymology. Cognates include Old Norse þreskjoldr, Swedish tröskel, Old High German driscufli, German dialectal drischaufel. Figurative use was in Old English.