Troth (noun)

1. A pledge of faithfulness, especially in a romantic relationship or marriage.
2. A promise or an undertaking, especially one made in a formal or solemn manner.
3. A pledge of faith or loyalty.

Origin:

The word "troth" comes from the old english word "truð" meaning "truth" or "faithfulness".

Examples:

1. He gave his troth to his bride at the altar.
2. He broke his troth by cheating on her.
3. The king demanded a troth of allegiance from his subjects.
4. The couple exchanged their troth in front of their families and friends.
5. The knight swore his troth to the princess.