Dragons are large mythical reptiles that are found all over the world. Well, the myths are found all over the world, anyway. Strangely, medieval naturalists were writing about and describing dragons for hundreds of years before they realized these animals did not exist. So where did the idea of dragons come from? Possibly from Homer's Iliad.
Six passages mention the drakon, a creature that, from the context, is clearly a snake. Homer didn’t seem to be referring to any specific type of snake and neither did Aristotle, whose fourth-century BCE History of Animals noted that the eagle eats drakons.
That explains the name, but how did Homer's snakes become winged monsters that breathed fire? That took some time, and came about because of assumptions, miscommunications, and the inability of writers to distinguish fact from fiction. Read some of the steps in the long process of turning snakes into dragons at Jstor Daily. -via Strange Company