knock-down

The compound "knock-down" is a transparent phrasal verb turned adjective/noun, formed from two native English elements. The verb "knock," imitative of a sharp striking sound, combines with the directional adverb "down," which originates from Old English terms for hill or descent. Literally describing the action of striking someone or something to the ground, its semantic logic is straightforward. Over time, this literal sense was extended metaphorically to describe prices reduced to a very low level and furniture designed to be taken apart and laid flat, both concepts sharing the core idea of bringing something from a higher to a lower state. This evolution showcases the productive nature of English compounding, where a vivid physical action generates abstract commercial and design terminology.

Structure: knock (to strike) + down (to a lower position) - knock: From Middle English knoken, from Old English cnocian ("to knock, pound"), of onomatopoeic origin. Its functional role is the core action verb. - down: From Middle English doun, from Old English dūne ("down, from a higher to a lower position"), originally a shortened form of "of dūne" (from the hill). Its functional role is an adverbial particle indicating direction or result.