Terp is also a shortened or slang version for interpreter, this is popular with the military. Example: "Can you get a terp to "translate" for us?"
This is not used as a put-down or in a bad way, although it is usually used in reference to a local citizen. This is just another way of shortening up words for use in the military lingo. Terp is probably also used like this in other areas, but this is the most prevalent use of it that I have seen.