This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium. Particularly: “Maybe from an unattested dialectal form of 犬? This is a weird word. I think it's likely a very old loan from Chinese, yet it has pretty much no attestation in Nôm texts, in fact, the oldest attestation I can find is in Việt Nam phong tục (1915). Granted, pre-20th century literature is probably not the best place to look for the word "puppy", but you would think that it was written down somewhere earlier in whatever lists and dictionaries that were there. I have also entertained the idea that this might be a loan from a non-Sinitc Trans-Himalayan language (which there're several cases for terms of animals, see bọ, dộc, ong khoái), but nah, they all pretty much lack the nasal coda (that STEDT/Matisoff reconstructed solely in account of the Sinitic reflex(es), and plugged it in their reconstruction for PTB).”