What are the origins of thestrals?

Question

In Harry Potter, there are magical creatures thestrals

A Thestral is a breed of winged horses with a skeletal body, face with reptilian features, and wide, leathery wings that resemble a bat's. . . . they are visible only to those who have witnessed death at least once (and fully accepted the concept) or due to their somewhat grim, gaunt and ghostly appearance.

J. K. Rowling has been known to reference Greek mythology in her work. For example, one of her characters is named Minerva, and her writing features mythological creatures such as a sphinx.

Is there a myth that explains the origins of these creatures? Which myth system would they come from?

Answer 1

I wasn't able to find any specific quotes from JK addressing this, but I did come across a post on MuggleNet from a contributor named Leah which speculated regarding a Celtic legend she happened upon in a bookstore. She explains the story in length, but summarizes it in this way:

Now, there are obvious similarities between [the main character's] mare and thestrals, such as their remarkable traveling abilities, their appearance, and their association with abstract things such as destiny, death, and magic. Rowling’s thestrals were carnivorous, which brings me back to the bird, kestrel.

Kestrels are mentioned in Quidditch Through the Ages as the name of a team, denoting that Rowling is familiar with them. Kestrels are dark birds of prey, with white patches below their eyes. Perhaps Rowling combined these birds with the mare of doom? One thing I also caught was N’oun Doare’s education by a Druid and his return at 17. Druids were ancient scholars and magicians who are believed to have practiced rituals in such places as Stonehenge. He reminds me very much of a certain young wizard…

I do not know if this is the story where J.K. Rowling discovered her intriguing creature, but one is allowed to speculate, no?

This seems a potential jumping off point for some further investigation, but of course not a solid answer.

Answer 2

I have a late answer. Some in the My Litle Pony fandom have tentatively referred to bat ponies as thestral and that's lead me down this rabbit hole... I study Old English as well for a fandom project. thester is Middle English for "dark, gloomy" from Old English thīestre. The -al ending is means "Of or pertaining to" from Latin. THEREFORE thester+al = thestral = A/one creature "Of or pertaining to the dark" To my knowledge there's no mythological creature called this but many creatures are named this way in other/older languages. Etymology is a wonderful thing!

Answer 3

In this article, we can see that Threstals were inspired from Horses. Let me copy the paragraph where it is highlighted.

While somewhat intimidating in appearance, these carnivorous horses are emblematic of a journey to another dimension, and reward all who trust them with faithfulness and obedience. Thestrals are native to the British Isles and Ireland, though they have been spotted in parts of France and the Iberian Peninsula; they seem to have an association with wizards who descend from the horse-loving Celtic peoples. Other parts of the world have their own equivalent to Thestrals