Jailer (noun)

1. A person responsible for the custody and control of prisoners in a jail.
2. A person who keeps someone as a prisoner.

Origin:

From the old french jailleor, jailleour, gailler, gaillour, from the latin cavellus, cavellarius, from cavea, cage.

Examples:

1. The jailer unlocked the cell and led the prisoner out.
2. The jailer was responsible for the prisoners' welfare.
3. The jailer had to be careful not to let the prisoners escape.
4. The jailer was accused of mistreating the prisoners.
5. The jailer was the only person who had contact with the prisoners.