The present participle of 'chine,' meaning to cut along or through the spine or backbone of a meat carcass, or to move with the spine or back in a certain direction.
From Middle English 'chinen,' derived from Old French 'eschiner' (to break the back), from Latin 'spina' (spine). The word literally refers to working with or separating the spine.
Butchers still use 'chining' today when preparing meat—it's one of those technical culinary terms that shows how medieval French influenced English food vocabulary, especially in fancy cooking.
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