Q: In relation to computer data, which is correct: “backed-up” or “back-upped”?
A: The simple past tense of “back up” is “backed up.” If you were to ask somebody about backing up (not “back upping”!) a computer document, for example, you might say, “Did you back it up?” and she might respond, “Yes, I backed it up.” (Not “Yes, I back it upped.”)
The term “back up” is called a phrasal verb—that is, a verb with two or more parts, like “back down” or “back off” or “back out.” The root (“back”) gets the “ed” ending. So, the somebody mentioned above would also say, “Yes, I backed it up” if she were talking about a pickup truck.
Bryan A. Garner, in A Dictionary of Modern American Usage, writes that the parts of a phrasal verb should be separate, not hyphenated (“backed up” instead of “backed-up”).You can read more about these multipart verbs in The American Heritage Dictionary of Phrasal Verbs.