The language is 'unfamiliar to' him. [=he does not know the language at all]
His 'unfamiliarity' with the language made the trip very challenging.
He gets nervous when he is in 'unfamiliar' surroundings.
(..) No, but-- Shh. Oh, good. Me neither. 'Cause there's nothin' wrong with bein' afraid. Fear's a sensible response to an unfamiliar situation. Unfamiliar dangerous situation, I might add. With a dragon that breathes fiire and eats knights and breathes fiire, (..)2001 Shrek