Buttery is traced as follows: The 'buttery-tasting' adjective is from butter + -y. The 'storeroom' noun is unrelated, from Old French boterie ('place for storing bottles or casks'), from botte ('cask, butt'). The historical trail runs through boterie in Old French. Morphologically, buttery is transparent: the 'buttery-tasting' adjective is from butter + -y. Used as an adjective and noun, buttery now means "tasting of or resembling butter; a storeroom for provisions or liquor", so the present definition can be read against the older forms and meanings. The same lexical family is also visible in related forms such as butter and butt. The result is a borrowed or transmitted form whose modern spelling carries a compact record of its route into English.