An Etymological Dictionary of the German Language/kosten
kosten (1.), vb., ‘to cost,’ from MidHG. kosten, ‘to come to, cost’; from MidLat. and Rom. costare (Lat. constare); Fr. coûter; see Kost (1) and (2); E. to cost.
kosten (2.), vb., ‘to taste,’ from MidHG. ‘to scrutinise, test by tasting’; OHG. and OSax. costôn, AS. costian (wanting in E.); a common Teut. vb. meaning ‘to put to the test, scrutinise, try.’ Kosten, like the Teut. words mentioned under Kost (2), is connected with kiesen, and is identical in form with Lat. gustâre, ‘to taste.’ Teut. kus, pre-Teut. gus, is the root. Comp. kiesen.