Real World article
(written from a Production point of view)

According to the script of the Star Trek: The Animated Series episode "Yesteryear", a dust demon was an atmospheric phenomenon near the surface of Vulcan.

Akin to small tornadoes, dust demons resulted from wind off the planet's desert plains occasionally swirling dust. The dust demons were neither referenced nor shown in the final version of "Yesteryear", and it is unknown how they vary from dust devils other than by name.