What name was Pokémon originally known by during its early concept stage?

During its early concept stage, Pokémon was originally known as Capsule Monsters.

Satoshi Tajiri imagined a game in which players could collect creatures and exchange them through the Game Boy Link Cable. The capsule idea reflected how the creatures would be stored and released, drawing partly on Japanese monster media and Tajiri’s interest in collecting small creatures.

Game Freak staff commonly shortened the working title to Capumon. Because “Capsule Monsters” could not be trademarked, the project was renamed Pocket Monsters. The name was later shortened internationally to Pokémon, a stylized contraction of “Pocket Monsters.”

The term “Pokémon” is therefore not the project’s earliest name. Capsule Monsters belongs to the development history, while Pocket Monsters became the Japanese franchise title and Pokémon became the global brand name.