'anorthitite' originates from the mineral name 'anorthite' combined with the suffix '-ite' (used for minerals/rocks); 'anorthite' itself ultimately derives from Greek elements (through New Latin/German mineralogical usage) where the element 'an-' means 'not' and 'orthos' means 'straight' (used in the original mineral name).

'anorthitite' was coined in geological/mineralogical literature by attaching the rock-forming suffix '-ite' to 'anorthite' (the mineral name). The mineral name 'anorthite' entered scientific usage via New Latin and modern European languages and was then used as the root for the rock name 'anorthitite' in English.

Initially the root term referred to the mineral 'anorthite'; over time the derived term 'anorthitite' came to mean the rock composed predominantly of that mineral.