'anorthic' originates from the mineral name 'anorthite' plus the English adjectival suffix '-ic'; 'anorthite' ultimately comes from Ancient Greek elements, specifically 'an-' and 'orthos', where 'an-' meant 'not' and 'orthos' meant 'straight/right' (used in forming the mineral name).

'anorthic' developed in modern English by deriving an adjective from the mineral name 'anorthite' (a New Latin/mineral name) through the addition of the suffix '-ic', resulting in the term used in mineralogy and petrology.

Initially used to denote 'of or relating to the mineral anorthite'; over time it maintained that specialized mineralogical/petrological meaning and is used to describe rocks or minerals composed of or containing anorthite/anorthosite.