Keyser was a pretty common Polish name amongst the DP's I met as a child (Busha was from south of Gdansk). In watching the movie, I thought it was a Polish gangster, not Turk. Was he Turk in the movie?
Yes, he was a Turk in the movie. The name Söze comes from the Turkish word sözel, which means “verbal”. That ties into Verbal Kint’s name in the movie, which was a big clue for Turkish speakers. Get it? :)