I can't really tell you why, but naming your character Frisk will alter your experience.
It's not really a big deal and it's not going to destroy the game, but idk, I guess there are people to whom it is important to get as much things out of a game as they can.
There is a thing that happens later, but iirc it won't if your character is named Frisk. It's a very minor thing that doesn't really have any effect on gameplay, and like, the game won't suddenly be unfulfilling or terrible without it. But I guess if you want to talk to others about the game after having played it, and discuss the meaning of certain scenes, it might be good to know what that thing is.