Archaic/transitive use meaning 'to naturalize' or 'to inhabit'; still attested in reputable dictionaries.
Definitionen
To grant the rights or status of a denizen; to naturalize. The act denizened the refugees, allowing them to own property.
To inhabit or populate (a place); to live in. Seabirds denizen the rugged cliffs year-round.
Synonyme
admit (to residence)
grant citizenship