Etymology: A common Germanic noun: Old English céap ‘barter, buying and selling, market, price, merchandise, stock, cattle’, = Old Frisian kâp , Old Saxon kôp (Middle Dutch coop , Dutch koop , Low German koop ), Old High German chouf , Middle High German kouf trade, buying and selling, merchandise, gain, payment (German kauf purchase) < West Germanic *kaup < Old Germanic *kaupo-z masculine; compare Old Norse kaup bargain, pay, wages (Swedish köp , Danish kjöb bargain, purchase, price), neuter < *kaupo^m . The original sense was ‘bargaining, barter, exchange of commodities’, whence, after the use of money, ‘buying and selling’, ‘buying or selling’, in later times often restricted to ‘buying, purchase’ alone. Beside it, the Germanic languages have the derivative verbs, *kaupjan (Old High German chouffen , Old English cíepan ), and *kaupôjan (Gothic kaupon , Old High German choufôn , Old English céapian ) to barter, buy and sell, etc. (see cheap v.), and Old High German an agent noun choufo , West Germanic type *kaupo , -on , trader, merchant. Old English is the only language in which the noun has the sense ‘cattle’, so that there is no ground for taking that as the original sense; it was either, like the word cattle n. itself, a special application of the general sense ‘merchandise, stock’, or perhaps connected with the use of cattle as a medium of exchange or measure of value; compare fee n.¹The coincidence of the stem kaup-, and especially the identity of the West Germanic agent noun *kaupo, -on ‘trader, merchant, dealer’, with Latin caupo, -ōn-em ‘petty tradesman, huckster, tavern keeper’, has suggested that the Germanic word and its family are of Latin origin. But there are serious difficulties. Some, taking the Gothic verb kaupatjan ‘to cuff’ as a derivative of the same root, suggest for kaup- the original sense of ‘stroke, striking’: compare the notion of ‘striking’ a bargain, ‘striking hands’ over a bargain, German handschlag.

Etymology: A comparatively recent shortening of ‘good cheap’, in its adjectival and adverbial uses; see cheap n.¹ 8 and 9; not found before 16th cent.

Etymology: A common Germanic verb: Old English céapian , -ode to bargain, trade, chaffer, buy = Old Saxon côpôn (Low German kôpen ), Old High German choufôn , Middle High German koufen to bargain, trade, buy and sell, buy, modern German kaufen to buy, Old Norse kaupa to bargain, barter, buy (Swedish köpa , Danish kjöbe to buy), Gothic kaupôn to traffic, trade, buy and sell < Germanic *kaupôjan , < *kaupo- , Old English céap , cheap n.¹ Beside this was another verb *kaupjan (not in Gothic), Old Low German côpian (Low German köpen , Middle Dutch côpen , Dutch koopen to buy), Old High German chouffen (Middle High German käufen ), Old English cíepan , cípan , cýpan , -te , to sell; this does not appear to have come down into Middle English. For the derivation, see cheap n.¹ This verb has now been superseded by cheapen v.