Star Trek: The Next Generation had to keep its distance from Star Trek: The Original Series, according to a rule by Gene Roddenberry
This caused an issue when Ira Steven Behr wrote the episode "Sarek." Producer Rick Berman would not allow him to use Spock's name...at least at first. Berman was keeping Roddenberry's rules to the letter, and In theStar Trek oral history,The Fifty-Year Mission: The Next 25 Yearsby Mark A. Altman and Edward Gross, Behr talked about how much of a struggle it was to write the episode. In fact, he called the fight to use the word "insane." [Via Screenrant]
To start, Behr said he was absolutely not allowed to use the word "Spock," and Berman made a big issue out of it. Even though the show had already tied into The Original Series by including Dr. Leonard McCoy on the first episode of the series, "Encounter at Far Point." But that was as much as was going to be allowed. Behr pointed out Sarek was Spock's father who had already appeared on Teh Original Series, but Berman still gave him a firm no.
Star Trek: The Next Generation writer had to fight to use the word "Spock."
A little later, while changes were being made to the script, Behr finally asked Berman "Rick, tell me again, why can’t we say the word ‘Spock’?" Behr said Berman's body language changed, and he could tell his boss didn't want to discuss the subject. But Berman finally relented and allowed the use of Spock's name one time in the entire episode.
It's strange to think that so much effort went in to keep the two series apart at the beginning of The Next Generation when, later on in the series, both Spock and Scotty appeared. Now, there's a connection between every Star Trek series, and that should be the case. Star Trek is all interconnected. Star Trek: The Original Series is the only series that could have existed (and did exist) without the others.