Literally, "his stub leg" or "his leg is a stub one", from emily "his leg" and kumpattk "which is short/broken off(?)", either from pattk (paattk) "is broken off" or from meputtk (mepuuttk) "is short".
Mesa Grande dictionary translates as if a verb: "has a peg leg (lit. short leg)", though it appears rather like a noun phrase.
Cuevas may or may not say this with the final "k".