A happy camper is, shockingly, someone who is happy.
While the term most likely existed at summer camps for years, the first time it was used in print to describe non-campers was a 1981 New York Times article. The article used the term to describe homeless people riding the city bus. By the very next year the phrase was adopted in the political arena and in television shows such as Silver Spoons. Since then it has made its way into most, if not all, English-speaking countries.
A related phrase unhappy camper is someone who is sad.
If you owned stock in a company on either side of a big deal, you likely came out of Monday a happy camper. [USA Today]
Nathan was keen to catch his first samsonfish. He did just that and landed his biggest fish ever. A very happy camper indeed! [ABC Perth]
If you googled ‘Of Mice and Men’ and ‘Reading Festival’ and were expecting a calm evening reflecting on the works of John Steinbeck on Saturday night, you would have been sorely disappointed. If, however, you knew that Of Mice and Men were in fact a California metalcore band whose distinctive brand of soaring melodies and thundering basslines, then you would have been a very happy camper. [Get Reading]
But there’s even less to be gained by starting him in place of a younger, now superior option. Perkins may even understand as much, potentially assuaging any concern that a reserve role would turn him into an unhappy camper. [Bleacher Report]