[Anime Project General Information] The term manga was created by the artist Hokusai, a prolific artist who lived from 1760-1849 and left over 30,000 works. He was the creator of the woodblock The Great Wave, his most famous picture and the one most closely identified with traditional Japanese art. His new term for some of his artwork was made of the words "man," meaning "in spite of oneself," "lax" or "whimsical," and "ga," meaning "picture."

The history of manga and Anime and a lot more on the subject in well documented essays over at the University of Michigan Japanese Animation Group's website.