ETYM A Latinism.
To call on or summon by a sacred name or in solemn manner; to implore earnestly; to adjure.

(Irregular preterit, past participle: swore, sworn).
1. To make a deposition; declare under oath; SYN. depose, depone.
2. To promise solemnly; take an oath.
3. To declare or affirm solemnly and formally as true
4. Utter obscenities or profanities
5. Have confidence or faith in