・Collins Dictionary: Earthling is used in science fiction to refer to human beings who live on the planet Earth.: At least this is how it is for most earthlings.
・Cambridge English Dictionary: in stories, a human being, especially when talked to or talked about by a creature from another planet: The writer found this especially true for the former of the two features, in which the earthling protagonist supplies his alien cohort with candy.
・Vocabulary.com: An earthling is someone who lives on the planet Earth. In science fiction books and movies, people are called earthlings to distinguish them from aliens. E.T. was definitely not an earthling.
You're most likely to come across the word earthling in fiction, since we more often refer to ourselves as "people" or "humans," assuming that we are all from Earth. In science fiction, though, some characters come from other planets or galaxies and aren't actually earthlings. Earthling has an Old English root, yrþling, or "plowman," and in 1949 the author Robert Heinlein first used earthling in a science fiction context.
原題を調べると、『地球星人』となっていました。SFですか、余り期待できないな。