Nishida said Pikachu’s name came from the Japanese words “Pika,” an onomatopoeia for the sound of an electric spark, and “chu,” the sound mice make.

The name is a combination of two Japanese onomatopoeic words that mimic sounds associated with the character: Pika – refers to the crackling sound of electricity or a sparkle of lightning Chu – imitates the squeak noise a mouse makes

From Japanese ピカチュウ (Pikachuu), derived from the onomatopoeic words ピカピカ (pikapika), a sparkly sound, and チュウチュウ (chuuchuu), a mouse sound. This is the name of a Pokémon, a yellow rodent-like creature who can summon electricity, from a series of video games starting 1996.

Series director Junichi Masuda stated that Pikachu's name was one of the most difficult to create, due to an effort of wanting to make it appealing to both Japanese and American audiences. The name is derived from a combination of two Japanese onomatopoeia: ピカ (pika), a sparkling sound, and チュー (chū), a sound a mouse makes.

The name "Pikachu" is derived from a combination of two Japanese onomatopoeic sounds, "pika" which is the sound an electric spark makes, and "chu" which is the sound a mouse makes.