Comments:KW 55, MGCD 161. Usually considered to be borrowed < Turk. bögsek (see Щербак 1997, 109, Лексика 278, EDT 329), but the Turkic word means "upper part of chest" which makes the loan theory extremely dubious. Mong. > Kirgh., Kaz. böksö 'buttocks' (see EDT 329), Evk. buksu etc., see Doerfer MT 130, Rozycki 37.