Gung-ho
Etymology
From Mandarin Chinese "gōnghé," a shortening of a phrase meaning "industrial cooperative" ("work together"). US Marine officer Evans Carlson adopted it as a unit motto in World War II, taking it to mean "pull together" and stamping it with the fervor of a rallying cry. English then generalized it to "zealously enthusiastic." Notably, the original Chinese phrase carried no such meaning — the enthusiasm is an American addition.
adjective · /gung-HOH/
Enthusiastically eager and wholehearted, sometimes to the point of overzealousness.
What it names
A quick label for unbridled, all-in enthusiasm — often with a hint that the eagerness may be running ahead of judgment.
Example
The new hire was so gung-ho about the launch that we had to remind her to actually sleep.
Related idea
Zealous is a steady, often principled intensity; gung-ho adds a raw, sometimes reckless eagerness.