The story
- Latin · derived fromopīnārī
- Late Latin · derived fromopinativus
- Middle French · derived fromopinatif
- English todayopinative
From opine + -ate + -ive. Middle French opinatif, and its source, Late Latin opinativus, from the participle stem of Latin opīnārī.
Etymology from Wiktionary, CC BY-SA 4.0.