'anorthositic' ultimately derives from the geological noun 'anorthosite' (coined in Neo-Latin/New Latin), where the element '-ite' denotes a type of rock and the earlier formation draws on Greek-derived components.

'anorthositic' formed in English as an adjective from the noun 'anorthosite' (entered English in the 19th century from New Latin 'anorthosites'), with the adjectival suffix '-ic' attached to denote 'of or relating to' the rock.

Originally the root term named a specific rock ('anorthosite'); over time the adjective 'anorthositic' came to be used to describe materials, textures, or compositions composed of or resembling that rock.