TFA says that a peryton, a class of astronomical signal, is named for a mythological beast, a winged elk. After first shuddering over the idea of an elk flying over one's head, I went to Google to find more about this as I've never heard of this beast before. Its source appears to be from author Jorge Borges who claims to have found a reference in an medieval manuscript. There appears to be no substantiating evidence elsewhere which is why it isn't as well known as other creatures of mythology.