So there is overlap between serpents and worms. I believe Okrand has even commented on this word, saying that originally he meant ghargh to mean anything like a serpent or a worm, just like the Old English word, but that when writers for Star Trek: The Next Generation writing the episode "A Matter of Honor" wanted a word for their newly invented plate of worms, they found ghargh, coached the actors to mispronounce it as gakh, and failed to notice the comma in the gloss, coming up with the new thing called serpent worms. Okrand later retrofit this mistake as qagh, accounting for both the mispronunciation and the wrong meaning. I don't have a citation for this information.