Surety (noun)

1. The state of being certain or confident about something.
2. A person or thing that guarantees the fulfillment of an obligation or the performance of a contract.
3. A guarantee or pledge, especially one provided by a third party for the performance of another.

Origin:

Derived from the old french word "surete" which means "security" or "assurance" it has been used in english since the 14th century.

Examples:

1. He gave his word as surety for the loan.
2. The surety of the contract is a bank guarantee.
3. The surety bond is a guarantee of performance on the contract.
4. She gave her surety that the project would be completed on time.
5. The surety of his promise gave her peace of mind.