Someone in the Trek tag asked a great question about the order of personal and family names for Vulcans. And I realized that in all my years of being a Trek fan I had never given it any thought. So I went to see what Memory Alpha had to say. I had never seen what the late, great Dorothy Fontana had said:
Jane Wyatt, who played Spock's mother Amanda Grayson, was once asked by fans at a convention what Spock's first name was. She replied, perhaps jokingly, "Harold" [12] However, the question itself was flawed, since the episode "Journey to Babel" makes it clear that "Spock" is Spock's personal name.
On the other hand, Spock's family name has never been established in canon. In the episode "This Side of Paradise", Leila Kalomi says to Spock, "You never told me if you had another name," to which he replies, "You couldn't pronounce it." D.C. Fontana – who was considered the "Vulcan expert" of the TOS behind-the-scenes staff and who created such details as the fact that Spock's father was an ambassador and his mother a school teacher – revealed, in an issue of the fanzine Spockanalia, that she had intended his family name to be "Xtmprsqzntwlfd", but since this is unpronounceable, there wasn't really any way to get this said in dialogue during an episode.
The Pocket TOS book Ishmael gives Spock's full name as "S'chn T'gai Spock".
This made me think of a head canon. What if Vulcans don't have a personal/family name combo like other races do? They're a telepathic species. They have a verbal use name like Spock, Sarek, or Tuvok. But they have a nonverbal telepathic name that contains the essence of who they are and their family relationships. Everybody with whom they have a close and thus telepathic bond knows this "name" but it's nothing that has any sort of verbal expression.