couste

It is a deverbal noun from Old French coster (“to cost”). The verb continues Latin cōnstō (“to stand firm; to cost”), a compound of com- and stō (“to stand”), of which only the sense “to be had for…

It is inherited from Latin costa (“rib, side”). The TLFi and Wiktionary instead call it a borrowing of the Latin anatomical word. Gamillscheg thinks the Latin word already had the transferred sense…