I've looked into this a great deal - it was the question that led me to folklore many decades ago - and I know of no supernatural creature/being that can be ascribed to a specific inspiration. This turns your secondary question on its head: as far as I am concerned all supernatural creatures/beings are without clear, singular inspiration.

The idea that there is "an element of truth behind every folk legend" - and by implication behind each of these creatures - is in itself an element of folklore that is not usually verifiable in reality. This line of thinking is referred to as Euhemerism, taking its name from the 4th century BCE Greek writer, Euhemerus. He asserted that the stories and beliefs in the gods grew out folk recollections of real people. By implication, we can search for "real" things that inspired other entities in folklore.

This idea is generally discounted by trained folklorists even while it is frequently embraced on the internet - and by many questions on /r/AskHistorians. One often finds explanations: elves and fairies are folk recollections of early, presumably short indigenous populations; trolls are recollections of Neanderthals; dragons were inspired by dinosaur bones or by a primal fear of snakes (so which one is it?); the cyclopes was inspired by an elephant skull; mermaids were inspired be seals of manatees.

These explanations are pure speculation, and there is no evidence that folk belief in the supernatural follows a path from the real to the extraordinary. Could these "real world" things contribute to belief? Perhaps, but that suggestion is also speculative, and proof to back up this idea remains elusive.

We must conceded that folklore is a broad river with many tributaries. It is possible that something from the real world could serve to reinforce and give strength to a belief, but just as it is not possible to determine the source of water downstream - which tributary is the source of the water in this bucket? - it is not possible to sort out how real-world factors may have contributed to folklore at one time of another.

It would be a tidy package to ascribe various supernatural beings to this or that cause, but unfortunately, folk belief and tradition doesn't work that way, and I would defy anyone to prove the opposite. Speculation is fun, but that is all it is.