An Etymological Dictionary of the German Language/Annotated/kaufen
kaufen, verb, ‘to buy,’ from Middle High German koufen, Old High German choufôn. The meaning in Old High German and Middle High German is somewhat more general, ‘to trade, negotiate,’ specially also ‘to buy, sell, or to barter.’ Compare Gothic kaupôn, ‘to trade,’ Anglo-Saxon čŷpan (Gothic *kaupjan), ‘to buy, sell.’ The word has numerous interesting meanings; its primary sense is ‘to barter,’ and was used by the parties on either side, and hence on the development of the system of paying in specie it signified both ‘to buy’ and ‘to sell’; compare also Anglo-Saxon ceáp, ‘trade, business, cattle’ (cattle was, in fact, the chief medium of payment in exchange; compare Geld and Vieh). It is most closely allied to Latin caupo, ‘retail dealer, innkeeper,’ and in connection with this fact it is certainly remarkable that a nomen agentis corresponding to Latin caupo is far less widely diffused than the Teutonic verb kaupôn (only in Old High German does choufo mean ‘shopkeeper’). The Teutonic verb in the form of kupiti, ‘to buy’ (allied to kupŭ, ‘trade,’ kupĭcĭ, merchant,’ Lithuanian kùpezus, ‘merchant’), passed into primary Slavonic and Finnish (kauppata, ‘to trade’). The cognates are wanting in Romance (compare Kaiser). — The Modern High German Kauf is Old High German chouf, masculine, ‘trade, business’; Anglo-Saxon čeáp, ‘trade’; in English the cognates cheap and chapman have been retained.