I finished Fairy Courts by Morgan Daimler, a look at fairy courts and culture in folklore. Some interesting takeways:
On the structure of fairy life:
“Although an argument can be made for the land of Fairy as well as fairies being territorial over human places, the social system doesn’t seem to be based on land ownership in the way human feudalism is. What we find instead is various references to belonging to specific groups and often to kings or queens, as well as a wider social structure that mimics, at least externally, the feudalism of Europe in the middle ages.”
"It's important to understand that when we talk about fairy courts we may be talking about two distinctly different things. This double meaning and usage comes from the Scots language where the word court means both a group attending on royalty and more generally any group or company. Because much of our folklore about the courts in a general sense comes from the Scots speaking areas of Scotland this double usage has found its way into modern fairylore, but a lack of understanding of the language means the nuance may be lost."
"The social structure here seems to have been a loosely feudal one, albeit a feudalism without the intrinsic land rights that define the human concept. Rather than the idea of a king or queen and nobles who own the land and are supported by tenant farmers we find that fairies' society was, in stories, based on pledges of fealty and service, through a hierarchical system with a king or queen at the top. In this version it is not land that is the baseline from which everything is worked but would seem to be scales of power."
"Fairy is a very feudal system[.....], everything is tied together through debts and obligations and what's owed to who. If you give to them then they owe you in return, even if that owing is paid back by not causing you mischief[.....]Reciprocity and obligatory return are the foundations of their society."
On fairy queens and kings:
"It may surprise some people to learn that while the idea of a Fairy King is relatively common today in older belief the emphasis tended to be on Fairy Queens, as we find, for example, in King James VI's writing. This may have represented an inversion of the power structures of the human world reflected in giving the greatest power to a female ruler rather than the male ruler common in the related human cultures. Due to this most of the references we have to rulers of the Scottish Fairy Courts focus on the queen or on a king paired with a queen."
"The Welsh Fairy Courts are somewhat unique among those found across Europe as they centre on a King rather than a Queen, and either don't have a queen or she is barely mentioned in the stories.
On how contemporary fiction influences belief:
"For many people in contemporary America popular culture and fiction form the basis of their knowledge of fairies, rather than traditional folk beliefs."
"Belief drawn from fiction feeds on itself, looking for reinforcement in additional literature, and perpetuating in digital media which will forward plotlines from novels and role-playing games into discussions of spirituality and belief."
"One example of this cycle of the folkloresque reinforcing itself and then becoming belief may be artistic, theatrical, and fictional depictions of small fairies with wings which are at odds with folkloric fairies that have long been wingless and flown through magic but have become so ubiquitous in mass media that they are now being reported in 20th and 21st century anecdotal accounts of fairy encounters."
"...In contrast the recent evolutions or changes in views relating to the [fairy] courts have been both swift, often happening within less than a decade, and also are rooted in fiction that is not coming from a culture that believes intrinsically in fairies as objective reality."
On the similarities and differences between humans and fairies:
"The Fair Folk in general are not humans and are not like humans; as Yeats would have it, they have few unmixed emotions and are beings of extremes, both good and bad. Often what they do seems perplexing to us, sometimes capricious and sometimes cruel. We cannot approach this subject expecting them to be or do what humans would in any circumstance but we must look at the system they operate in as a guideline to understand their etiquette which is distinct from our own."
But, there are surface similarities, particularly in Scotland:
"In almost all ways the fairies of Scotland are similar to humans, except with a greater magical ability. They may look much like a human being and often act, or try to act, human, yet are able to command magical powers and may do things that seem inexplicable or cruel."
"It is well-established across folklore that fairies are, despite an often-human appearance, foreign beings from a foreign culture."
So human-looking fairies did not originate in ACOTAR. Yet it is important to keep in mind that this similarity in appearance does not mean they are human:
"Fairy reactions in situations may not match expected human ones, they may seem too minimal or too extreme, and fairies are often described as cruel. Through this lens then we must try to understand fairies not as morally good or bad, by human standards, but as being who exist outside of human morality."