gung ho

Inf. enthusiastically in favor of something. Bobby is really gung ho on his plan to start his own company.

Also, gung-ho. Extremely enthusiastic or dedicated, as in She was gung ho about her new job. This expression was introduced in 1942 as a training slogan for a U.S. Marine battalion, derived from what an American officer thought were Mandarin Chinese words for "work together." It was actually an abbreviation for the name of Chinese industrial cooperatives.