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.
(..) - I will speak for captain Nero. Then ask captain Nero: What gives him the right to attack a Federation vessel. Do you know the location of ambassador Spock? I'm unfamiliar with ambassador Spock. - What is the current star date? - Star date? Where are you from? Terminated. (..)2009 Star Trek