prisionero
/pɾisjoˈneɾo/ · A2 · noun · m
prisoner
⛓️ prisión + -ero = prison + -er: the one kept in prison
Built just like English prison → prisoner. Prisión is prison, and the suffix -ero marks a person tied to that thing (as in carcelero, jailer). Both words go back to Latin prehensio, a seizing: a prisoner is someone seized.