I know that the Vulcan nerve pinch was first shown on Star Trek, now my question is: when was it first shown in the printed page? It’s mostly academic, but other people might find it interesting.
Each of the original series episodes received a novelisation by James Blish. These were released almost contemporaneously with the TV show. Star Trek 1 was the first ever Star Trek tie-in novel and was published in 1967, just six months after the episode TOS: The Naked Time was broadcast. It contains the following passage.
“Sorry, neither,” Uhura said. She threw a glance deliberately over Sulu’s left shoulder; as he jerked in that direction, Spock’s hand caught him on the right shoulder with the Vulcanian nerve pinch. Sulu went down on the deck like a sack of flour.
The first reference to the nerve-pinch in a non-novelisation fiction book is in Spock Messiah from 1976, the second Trek tie-in novel not based on a specific episode.
“Problems,” she said unhappily. “Less than an hour ago, a tall hillman wearing a black and red clan mask went into Chag Gara’s house. When he came out, he was carrying a figure wrapped in a blanket over one shoulder. Ker said a couple of the neighbors tried to interfere, but the hooded man paralyzed them with just a touch. So they let him carry Chag Gara away.”
“The nerve pinch!” McCoy burst out.
“Yes,” Kirk said nodding somberly. “It has to be Spock. Only a Vulcan can do that, and now he’s got Gara.”
Interestingly, the first tie-in novel not based on an episode (Spock Must Die!) also heavily featured Spock, but had no nerve-pinching.
Reposting Valorum's comment as an answer:
Novelised versions of Star Trek episodes were published around the same time they were screened: https://en.wikipedia.org/wiki/Star_Trek_(Bantam_Books). So this is likely the first literary appearance.