What does the word oath mean?

Usage examples for oath

  1. Why should I take the oath, General Butler? – A Daughter of the Union by Lucy Foster Madison
  2. They would not have caught us alive, you may take your oath. – Colonel Thorndyke's Secret by G. A. Henty
  3. I could take oath to that. – The Valiants of Virginia by Hallie Erminie Rives