Eyeing the game’s success in Japan, Namco initialized plans to bring the game to the international market, particularly the United States.[26] Before showing the game to distributors, Namco America made a number of changes, such as altering the names of the ghosts.[26] The biggest of these was the game’s title; executives at Namco were worried that vandals would change the “P” in Puck Man to an “F”, forming an obscene name.[12][33] Masaya Nakamura chose to rename it to Pac-Man, as he felt it was closer to the game’s original Japanese title of Pakkuman.[12] In Europe, the game was released under both titles, Pac-Man and Puck Man.[34]

Source: Wikipedia