Endorser (noun)

1. A person who formally approves or supports something, such as a product, service, or candidate.
2. A person who signs the back of a check or other negotiable instrument to transfer or authorize transfer of the instrument to another person.

Origin:

From the verb "endorse" meaning "to approve or support".

Examples:

1. The celebrity is a well-known endorser of the fashion brand.
2. The political candidate has gained a lot of support from famous endorsers.
3. The endorser signed the back of the check to authorize the transfer of funds.
4. The endorser must be a signatory of the account in order to authorize the check.
5. The endorser must endorse the check before depositing it into their account.