Greninja

Greninja is the final evolution of Froakie, a Water/Dark-type frog Pokémon introduced in Generation VI (Kalos region). It fights with the speed and cunning of a ninja, creating compressed water shuriken to slash opponents and moving so swiftly it can appear and vanish before enemies react. Greninja gained particular fame as the signature Pokémon of Ash Ketchum in the anime, where its unique 'Ash-Greninja' form highlighted a deep bond between trainer and Pokémon.

The Japanese name ゲッコウガ (Gekkouga) likely combines 月光 (gekkou, meaning 'moonlight') with elements suggesting a ninja or frog, where the final 'ga' (蝦/ガ) can evoke 'gama,' an old word associated with toads/frogs in Japanese folklore. The English name 'Greninja' is a portmanteau of 'green' (referencing both its frog appearance and coloration cues) and 'ninja,' directly reflecting its Ninja Pokémon category. Both names emphasize its stealthy, ninja-like nature paired with its amphibian (frog) basis.