The mystery is over, thanks to this all-encompassing feature by GameXplain. Here is something I did not know until today: The etymology of "Moblin". It's derived from the Zelda brutes' name in Japanese, which itself comes from the Japanese words for "Forest" and "Goblin".
You may remember they were called "Molblins" until A Link to the Past. Incidentally, that's when they shifted away from their bulldog appeaerance to a more porcine countenance. That also corresponds to the overall story development of the series, in which Moblins, by becoming true followers of Ganon, start mimicking his appearance.
[h/t Robert P.]