'plagioclase-bearing' is a compound of 'plagioclase' + 'bearing'. 'Plagioclase' ultimately comes from Greek elements 'plágios' meaning 'oblique' and 'klasís' meaning 'breaking' (referring to oblique cleavage), and 'bearing' derives from Old English 'beran' meaning 'to carry'.

'plagioclase' entered scientific vocabulary via New Latin/German mineralogical usage (e.g. German 'Plagioklas'), formed from Greek roots, and was combined in modern English with 'bearing' to describe rocks that 'carry' or 'contain' plagioclase minerals.

Originally the components referred literally to 'oblique break' (for the mineral's cleavage) and 'to carry'; together in modern usage the compound describes material that contains plagioclase.