The original working title of the Pokémon games was Capsule Monsters.
Satoshi Tajiri’s early concept used the idea of creatures stored in capsules and released for battles. The title later changed to CapuMon and then KapuMon before becoming Pocket Monsters, the Japanese name used for the franchise. Trademark concerns influenced these changes during development.
The capsule idea remained visible in the finished games through Poké Balls, the items Trainers use to catch and carry Pokémon. The final English brand name, Pokémon, is a shortened form of Pocket Monsters with an acute accent added over the e to guide pronunciation in international markets.
The working title is sometimes confused with the final Japanese name because both refer to the same basic concept. Capsule Monsters was never the public title of the released games. It was an early development name, while Pocket Monsters was the name used for the Japanese launch in 1996.