The Pokémon video games used the name Pocket Monsters in Japan.
The Japanese titles for the first games were Pocket Monsters Red and Green. The international brand name Pokémon is a shortened form of “Pocket Monsters,” using the Japanese romanization Poketto Monsutā.
The title changed during development. The project was initially called Capsule Monsters, then went through forms including CapuMon and KapuMon before settling on Pocket Monsters. Trademark concerns were part of the reason for the changes, and the final Japanese name became the foundation for the franchise's identity.
Outside Japan, the games were released as Pokémon Red and Blue rather than Red and Green. The change helped avoid confusion over color names and reflected the international branding. “Pocket Monsters” still appears in references to the Japanese anime, games, and franchise history.