The pop star made the bizarre plea to us earthlings during an interview with Australian outlet PEDESTRIAN.tv -- in which they say the term "alien" itself is offensive ... even as it pertains to actual would-be aliens from outer space ... who may or may not be zipping around above us.

The context here is that Demi is plugging this new Peacock special of theirs called "Unidentified" ... where they and their pals go looking for proof of Martians, and seem to find something.

While talking shop on their E.T. project, they said this ... "I really think that if there was anything out there that would want to do that to us, it would have happened by now. But, I think that we have to stop calling them aliens because aliens is a derogatory term for anything." DL adds, "That’s why I like to call them ETs! So yeah, that’s a little tidbit. A little information that I learned."

It doesn't sound like Demi got this intel from the actual mothership or anything ... so it's unclear if aliens are, in fact, outraged by humans referring to them as "foreigners," which they would be by the word's definition.

Of course, the term does carry a negative connotation when applied to actual people -- like immigrants to the U.S., for example -- which is why some have called for phrases like "undocumented" and the like to be used instead ... as it's more kosher.

With that said, Demi demanding we nix the term -- one that's been used for at least a century or more in this country -- when talking otherworldly beings ... it's absolutely absurd.