Hysteron proteron is a figure of speech in which you put the last thing first and the first last, reversing the logical order. Whenever you say, "I'm putting on my shoes and socks," you're using hysteron proteron (unless you actually put your shoes on first!).
This rhetorical device gets its name from a Greek phrase that means "later earlier" or "the latter put as the former." When you use a hysteron proteron, you switch things up, usually to emphasize something (it's the shoes that are important, although the socks actually come first). If you're furious at your brother, you might use hysteron proteron by exclaiming, "I am going to murder him, and then I'm going to make him give me back my laptop!"