Thank you all!
@ Therin/Christopher, watching "This Side of Paradise" was what prompted my search and question here. *g*
Yeah, I re-read the quotes on Memory Beta and it reminded me that Spock hadn't actually told her. That sectiion is rather messy, with all those references clumped together, essentially forcing researchers to read each book to sort out which factoid belongs to which resource.
By the way, in issue 2 of Spockanalia
, the first Star Trek fanzine, Dorothy Fontana revealed that she had arbitrarily assigned Spock the family name "Xtmprsqzntwlfd". This name also turned up in the semi-pro, fan-produced "USS Enterprise Officers' Manual". (And, coupled with a humorous convention comment by Jane Wyatt, this is actually a first name and the pronunciation is "Harold".)