'annunciative' originates from Latin, specifically the verb 'annuntiare' (later spelled 'annuntiare'/'annunciare'), where 'an-' (from ad-) meant 'to/toward' (assimilation) and 'nuntiare' meant 'to report or announce (from 'nuntius' meaning 'messenger').

'annuntiare' in Latin passed into Old French forms (e.g. 'anoncier'/'annoncier') and Middle English as 'announce' and the noun 'annunciation'; the adjective 'annunciative' developed from these forms to mean 'relating to an announcement' or 'relating to the Annunciation'.

Initially it was connected to the action 'to announce' or 'to report'; over time it came to be used both for things that announce (annunciative = announcing) and for things relating specifically to the Christian 'Annunciation'.