'anti-Gnostic' originates from Greek: the prefix 'anti-' (Greek 'αντί', anti-) meaning 'against' and the word 'gnostikos' (Greek 'γνωστικός') meaning 'relating to knowledge' (from 'gnōsis' 'knowledge').

'Gnostic' entered English via Late Latin/Medieval Latin and New Latin from Greek 'gnostikos' ('knowing, relating to knowledge'); the combining prefix 'anti-' comes from Greek 'anti-' ('against'). These elements were combined in English to form the compound 'anti-Gnostic' to denote opposition to Gnosticism.

The parts originally referred literally to 'against' + 'knowledge/knowing' (i.e., against the Gnostic movement or its claimed special knowledge). Over time the compound has been used specifically to mean 'opposed to Gnosticism or Gnostic doctrines' rather than a literal opposition to knowledge.