In addition to Charles Xavier heading up the team, it just so happens that the mutant gene shared by all X-Men is the X-Gene, which is the source of their various powers. On top of that, the government’s secret Weapon X program has birthed the likes of Wolverine and Deadpool. The X-Cutioner is a Marvel villain who hunts mutants. The list goes on and on.
The reasoning behind the X-Men’s title has changed over the decades. In the 2000 movie, for example, Patrick Stewart’s Professor X says that his students chose the name themselves. But while the inspiration for the name can shift from writer to writer, its true origin was laid out in 1963. The popularity of the “X-Men” series is likely what retroactively led to the letter “X” popping up all across the Marvel Comics universe. Things like the Weapon X Program — and, by extension, Wolverine — arguably wouldn’t exist without the team’s title. And it all was because Professor X was having some fun with wordplay.
