Ah, you are correct. I always assumed 'This Side of Paradise' was referring to a Vulcan first name, but Laila just said "another name", meaning it could have been a surname.That's not his "real" name, it's just the family name (as Amanda points out in "Journey to Babel" when Kirk tries addressing her as "Mrs. Sarek"). Spock is his given name. In the West, we're used to people being formally addressed by their family name/surname, so "Mister Spock" would seem like the equivalent of "Captain James" instead of "Captain Kirk." But there are societies where the given name is the primary one to use even in formal address, e.g. in Arabic or Vietnamese.