jailer
From Longman Dictionary of Contemporary Englishjailerjail‧er (also gaoler British English) /ˈdʒeɪlə $ -ər/ noun [countable] old-fashioned PRISONsomeone who is in charge of guarding a prison or prisonersExamples from the Corpusjailer• But through the news media, Arpaio has managed to recast the image of county jailer into that of Wild West sheriff.• A lonely jailer places desperate advertisements for a wife.• The provodnik, my jailer, showed a young bearded man into my compartment.• He is not only a prisoner but is conditioned to be his own jailer too.