This is interesting, there is another Sardinian noun with the same meaning, that could have arrived in Sardinian from Greek language, during the Byzantine age. Or it could be a residue of pre-IE languages.Figuratively, we have the expression «κρατάω μούτρα» [kraˈta.ɔ ˈmu.tra] --> lit. to hold face; «μούτρα» (neut. nom. pl.), is the colloqualism of face in MoGr (mug?) < Byz. Gr. «μοῦτρον» moûtron (neut. nom. sing.), «μοῦτρα» moûtra (neut. nom. pl.) --> face(s), of uncertain etymology.