Greetings!
Okay, so to start, these are pretty fun. They look like starfish!
A wild hennin has appeared!
Ahem.
I looked in Google Books for henins*, and the only references to the “triple-horned” variety seemed sketchy – meaning they didn’t have citations. it looks like the origin of this image and concept is from a variety of ladies journals from the 1880s. Yay Victorian myths about 15th century clothing.
But just in case, I reached out to a newly-minted Laurel who is known for her hats. She didn’t know of anything, nor could she find any solid research for this type of hat.
Sorry. 🙁
It looks like we’ll have to keep looking for ideas for 15th century Staryu cosplay.
*Google Book is a great place to start research, by the by, since it searches the full text of a book, whether you can see those scanned pages or not. It helps you refine terms and points you toward possible sources. I kind of adore it.
My hat is off to you as you continue your research into fancy headgear.