The Origins of Fairies
Continuing with my series on the origins of stuff, here's one that's actually quite close to my heritage - fairies, or the Fae, or changlings. Fairies were a kind of catch-all reference for otherworldly spirit beings, typically connected to pre-Christian pagan myths and nature beliefs. The etymology of the word 'fairy' comes from 'faerie', which drives from the Latin word for enchantment, and so fairies have always had a strong implication of magic.
The Fae Evolution
Before the scientific method became more widespread among the beer-drinking classes, it was usual to attribute inexplicable phenomena to spirits or other magical beings. The presence of flint arrowheads from the Stone Age in Britain and Ireland (so-called 'elf-shot' at the time) seems to have contributed to the fairy mythos, and so there are strong overtones of fairies being an older race with mysterious powers, pushed out to the fringes by the expansion of humanity, and connected to nature.
The detail about stone arrowheads being called elf-shot is interesting, because it suggests that that's the origin of the cold iron part of the trope. Legend has it that cold iron is harmful to fairies, and they will not use it. Perhaps that was the best explanation people had, centuries ago - surely the fairies used stone because they couldn't use iron!
But where did the idea of wings come from? This is certainly not essential, as there are fairies who don't have wings (such as leprechauns) but it's certainly a feature of the classical fairy model. It seems to have come from an embellishment from Canto II of Alexander Pope's The Rape of the Lock:
He summons strait his Denizens of Air;
The lucid Squadrons round the Sails repair:
Soft o'er the Shrouds Aerial Whispers breathe,
That seem'd but Zephyrs to the Train beneath.
Some to the Sun their Insect-Wings unfold,
Waft on the Breeze, or sink in Clouds of Gold.
Transparent Forms, too fine for mortal Sight,
Their fluid Bodies half dissolv'd in Light.
Pope wrote this in 1714, but the presence of cherubs or cupids was well established before then, so the concept of small, flying humanoids was not unusual. He refers to these here as sylphs; a 'sylph' has become another fairy-related word. But why insect wings? Well, I think it's just a convenient embellishment to the story. Pope imagines the sylphs as guardians of a virgin noblewoman, and I can only think that he found it funny to write about a woman with a cloud of annoying little creatures buzzing around her!
It's interesting that Pope's poem describes the modern fairy almost exactly, so it's worth noting just how influential he was on the visual concept. Read Canto II here if you're curious.
In Irish Legend
In Ireland, the fairies are considered to be a race in their own right, with their own customs and culture, and they are known to be capricious and flighty in their ways. There are a few different components to the fairy mythos that are very much Celtic and Irish in nature.
(Note: I'm speaking in the present tense because the belief in fairies is still pretty strong in Ireland. There's innumerable superstitions and folk-tales about them and the places that supposedly 'belong' to them.)
The leprechaun is the most well-known trope related to fairies in Ireland, but it's also a rather horrible one. The image of the little troublemaker, dressed in green and ready to make mischief, seems to have evolved out of negative stereotypes of Irish people themselves. There are other interesting details, such as that of the leprechaun having to grant three wishes if he is caught - a callback to the Irish géas, if nothing else - that are very much un-fairy-like and more Irish-like.
The main body of fairy folklore in Ireland derives from the Tuatha Dé Danann, the ancient inhabitants of Ireland who reputedly had incredible magical gifts. They were considered gods and goddesses (indeed, the name of Ireland derives from them: Ériu = Éireann = Ireland) and there are stories of them littered all over Irish mythology. Over time, they evolved into the Sídhe, the 'people of the mounds' - meaning fairy mounds, which were actually the remains of Iron Age ring forts. Funnily enough, they never seemed to gain wings in Ireland.
These days, fairies have metamorphosed into a kind of broad grouping of magical beings of a European flavor that aren't explicitly related to some kind of religion or pantheon. The typical tiny-humanoid-with-butterfly-wings iconography found its way into children's media through Victorian fairy-tales, and has been a mainstay there ever since. But the tropes of the Tuatha Dé Danann, of powerful beings holding court and ruling over lesser creatures, have found their way into more adult interpretations of fairy mythos. Various elements of central European folklore around elves and dwarves have also been rolled into the mythos, and there's a lot of fluidity between them.
I personally credit White Wolf's Changling RPG series from 1995 as the spark for a lot of modern adult fantasy involving fairies. (That's another subject close to me - I played Changling in college.) The mythos is still evolving beyond the original tropes and it certainly hasn't been as overdone as zombies, so it'll be interesting to see who takes it where next.