'Gnostic' originates from Greek, specifically the word 'gnōstikos', where 'gnōsis' meant 'knowledge'.

'Gnostic' passed into Late Latin as 'gnosticus' and then into English (via scholarly and theological Latin usage) as 'Gnostic', becoming established in English usage by the early modern period.

Initially it meant 'relating to knowledge' (from the Greek sense of knowledge), but over time it came to be used especially for the religious movement and its adherents, i.e. 'relating to or belonging to Gnosticism.'