What a trooper!
Does this phrase look correct to you? It’s okay if it does because using trooper instead of the correct word is a very common mix up.
In the phrase above, you should use trouper instead of trooper.
A trouper is a person who is a member of a troupe (a group of performers, such as actors). A trooper is a soldier (a member of a group of troops), a police officer (such as a state trooper), or a person in a similar category of jobs.
We use trouper in the phrase above and similar phrases (such as he is such a trouper) when we refer to a person who has overcome obstacles. The popular phrase the show must go on comes from the idea that even if bad things happen (a piece of the set breaks or an actor has a sore throat), the troupe must continue with the show—lest they be pelted with tomatoes coming from angry audience members.
When you refer to someone as a trouper, you are giving him or her a compliment and saying in short that even though the s/he has had bad things happen, s/he has continued on and worked to overcome the obstacles. The show must go on.
A student who has a bad cold and still shows up to take the big test is a trouper.
A runner who stubs his toe in the middle of a marathon and keeps running is a trouper.
A dancer who falls in the middle of her big solo and continues on with the routine is a trouper.
A person who is fighting a serious illness is a trouper.
Blame it on the French
One reason for the trooper and trouper confusion is because both words come from the same root word, troupe. The Middle French language gave us the word troupe, which then meant a band of people. In the 1540s, English got troop (and thus trooper) from this word, adapting it to mean a body of soldiers. Then, in the 1820s, we began using troupe in English to mean a group of performers, a member of which is a trouper.
*I got this etymology information from a website I absolutely love, called Online Etymology Dictionary. If you ever are interested in learning the history of a word, I encourage you to visit this site for a thorough and easy-to-understand explanation.