I always thought of "Earthling" as a fairly modern sci-fi type of word but I've learned from the excellent "Words Unravelled" podcast and YouTube channel that it was already word in Old English. It meant a ploughman and was still used in that sense until the early 1800s. From about 1600 it came to have the modern sense of someone who lives on the Earth.
It's interesting because it uses the suffix -ling, which has several loosely related meanings. Originally in OE it (usually) implied a person concerned with or related to some particular thing (hence earthling) and we also have hireling (someone hired) and sibling (originally a kinsman, now just a brother or sister of course, and I used to think it was just a modern word, but not so). Starling the bird also seems to use the same construction, and birds crop again below
Nowadays it can just be a diminutive, as in gosling, duckling, sapling or nestling, but can sometimes also have dismissive connotations, the OED gives the examples godling, lordling, kingling, princeling. A princeling is definitely some way down the scale of princeliness (yes it really exists).
Chat GPT threw up quite a few more: weakling, fledgeling, hatchling, seedling, underling, yearling, changeling, foundling, stripling, mostly implying some sort of smallness or weakness.