the older irish name for the town was "baile chaisleáin ua bhfoirchealláin" (meaning "castle-town of uí fhoirchealláin"). this has been anglicised as "ballycashlan-offerillan" and "ballycaslane-offeralane". uí fhoirchealláin is the name of the parish and was added to distinguish it from another castletown.