'porphyritic' originates from Greek, specifically the word 'porphyra', where 'porphyra' meant 'purple'.

'porphyritic' developed via New/Modern Latin and English from Greek 'porphyra' → Late Latin/Medieval Latin 'porphyrites' (porphyry) → English 'porphyry', and the adjective form 'porphyritic' was formed in geological usage to describe rocks with the appearance or qualities of porphyry.

Initially it referred to the purple color of the stone ('purple'), but over time it evolved to describe the textural characteristic of certain igneous rocks ('having conspicuous larger crystals in a finer matrix').