What is the original full name behind the abbreviation “Pokémon”?

The original full name behind “Pokémon” is Pocket Monsters.

In Japan, the franchise began as Pocket Monsters, written as ポケットモンスター and commonly abbreviated to Pokémon. The abbreviation uses the first part of “pocket” and the first part of “monsters,” with an acute accent added to the e in international branding to guide pronunciation.

The name reflects the original concept of carrying collectible creatures in a pocket-sized Game Boy. Players could store Pokémon in the game's Pokédex, train them, and exchange them with other players through the link cable.

“Pokémon” is also used as both a singular and plural noun in official English usage: one Pokémon and many Pokémon. The short form became the worldwide brand name as the games, anime, cards, films, and merchandise expanded beyond Japan.