In his analysis of the first game in the 2018 world championship, Antonio Radić says that on move 9. ... b7-b6, Carlsen took six minutes to make a move that he probably already knew:
And now Carlsen again goes b6, but it did take him some six minutes for this move. As the other moves Carlsen played relatively quickly, so I don't think this is a new position for him. I think he actually came very much prepared and he was just like a Botvinnik moment, where he takes six minutes to think about a move he already prepared.
The only other instance of "Botvinnik moment" was in a comment on the game Raymond Keene vs Mikhail Botvinnik, Hastings, 1966-1967. The annotation for the last move says, "At which point Botvinnik gasped, raised his hand to his forehead, and resigned," and a commenter added, "We have all been there and had this Botvinnik moment."
This is clearly not what Agadmator is referring to. Was Botvinnik really known for taking a relatively long time for moves that he had prepared? Is "Botvinnik moment" a common phrase for this?