What was Pokémon originally called in Japan before the English name was adopted?

Pokémon was originally called Pocket Monsters in Japan.

The Japanese title is Poketto Monsutā, written as ポケットモンスター. The English name Pokémon is a shortened form of that title, using an acute accent to indicate the pronunciation and distinguish the brand internationally.

The name reflects the original concept of carrying collectible creatures in portable devices, particularly the Game Boy. In Japan, the first games were released as Pocket Monsters Red and Green, while international releases used Pokémon Red and Blue in most regions. The name is sometimes mistaken for a completely different title, but Pokémon is an internationally adapted abbreviation of Pocket Monsters rather than an unrelated replacement.