What name was Pokémon originally known by in Japan?

Pokémon was originally known in Japan as Pocket Monsters.

The Japanese title is Poketto Monsutā, written ポケットモンスター. The shortened form Pokémon became the internationally recognized brand name and is also used extensively in Japan.

The name reflects the original concept of collecting monsters that could be carried in Poké Balls. The franchise began with video games, but the name soon covered animated television, trading cards, merchandise, films, and other media.

The acute accent in Pokémon comes from the shortened English spelling. It helps distinguish the final vowel sound and is part of the official stylization, although many informal references omit it.