All I can tell you is I just trawled all 166 episode's summaries on the
TV to me Flintstones guide which includes most associated trivia (including the 5th episode where Betty was called 'Elizabeth' for the only time). I also found another forum where someone posted the same question almost a year ago, but believe it or not they use email to get their answers, so I don't know if he ever got one. I can also add another little known fact from the site, the pilot episode was called 'The Flagstones', but was never shown, though a little was used later on. I hope (unlike Quincy, Lovejoy and Colombo's first names which also took up a deal of my investigation) there actually is an answer to this one, and I didn't even start the Jetsons...