Sowas findet man ganz schnell auf Wikipedia. Hier sind alle Charaktere vorgestellt: http://en.wikipedia.org/wiki/Characters_of_Elfen_Lied
Da findet sich der Abschnitt:
Notes: nyū (or more commonly gyūnyū) means "milk" in Japanese. The character is called "Nyū" because, when Kouta and Yuka first meet Lucy on the beach, this is the only word she is capable of saying. Some anime fans compare this childlike state to Chi, the female lead of Chobits, where when she is activated, the only word she can say is "chi", and her vocabulary later grows, much like Nyū's.
Das schreibt sich dann 乳 (Nyuu).
Grüße,
- André
