The history of our encounters and interactions with the Faefolk are marred by misunderstandings and misinformation, violent distrusts born of baseless fears and paranoia.
Although the word namelings also has a mundane, though admittedly little-used, definition - referring to two or more people who share the same first and family names (at least) - it is also considered the more proper term for the creatures that, in most folklore, are called changelings. According to the myths about the various faefolk, in which the phenomena is widely misreported and wildly misrepresented, changelings are infant faeries who have been left in the place of human babies that have been stolen away for any number of nefarious purposes. Such misapprehensions and plain fabrications - wherein the babies are intended to be raised as chattel, to continue otherwise infertile faerie bloodlines or are simply delicacies doled out diplomatically in the service of Faewildes statecraft - have led to a great deal of understandable but unnecessary animosity.
Humanity and the various inhuman occupants of the Faewildes (another reality, our nearest neighbour in some regards, which has historically bordered and breached our own most commonly and most frequently in western Europe) are mutual victims of half-truths and misunderstandings that have been spun, albeit fearfully and often absent malice, into the basest propaganda. While it can be difficult, if not impossible, to properly ascribe motivation even to our peers and closest allies - let alone to intelligences that are ancient, functionally immortal and fundamentally alien to our own - where the changelings of myth represent trickery (a transactional value given to our most innocent and most precious), the existence of a nameling is, as near as can be told, intended as a kindness; even if it is a kindness that not all would choose to receive.
Acutely empathic, faeries do not appear to have or use language as we might understand it - arguments having been made that their communication might be more psychic than physical - and they seem to be particularly closely attuned to recognising pain in other living creatures. Sometimes in, but never truly of our world (continued exposure to whose physical and emotional toxicities is a slow but certain death sentence) they nonetheless react to our keenest pains, occasionally before we have even begun to feel them. Prognosticating, pre-trauma, faeries can sense the imminence of deaths - though whether they feel each and every one or are only responding to the presence of something specific to certain instances is a matter of some debate - and, in some cases, forestall grief by replacing a person who is going to die with a nameling.
Unlike Fetchfires, magical simulacra created as sacrificial offerings that will suffer or die in someone else’s place, namelings cannot (or at least are not intended to) circumvent the inevitability of whatever events are already in motion: Once Faeries sense the unbearable hurt that will be caused by someone’s imminent death - whatever obscure metrics or criteria these are, we know that they seem only to be triggered by natural causes and not accidents or other violence - they spirit the ill-fated person (be they infant or adult) to the Faewildes and leave a nameling in their place. Just as our world would be eventually lethal to any faerie who had not been suitably transformed, the Faewildes are incapable of sustaining human life; the air induces a state of euphoria, the waters a deep and abiding catatonia in which slumber a person will meet their death in bliss.
Changelings are named as such because of the assumption that they are essentially imposters; that it is merely their form that has been altered in order for them to pass as the person they are replacing. The term nameling is used not only because it provides a degree of separation from these associations, but because of the nature of how they come to be and what they share with those who might fairly be called the original or the source person: A faerie who chooses to be a nameling gives up their home, their immortality and every aspect of their self and - by imbuing their resultant blankness with an essence part borrowed from nomenclature (the Faewildes operating in part on magical laws which see names as the source of self, strength and identity) - become someone and something else entirely.
The nameling is not the original, but even beyond philosophical conversations around the continuation of the self there is a degree of shared existence that makes them more than a copy. Even for the period in which they exist alongside one another, the original person and their nameling share something intangible and eternal, souls shared and entangled. In the end, some have argued, the only life that is really lost - in any sense that means anything - is that of the faerie who has chosen to cross worlds in order to spare strangers the hurt of losing someone whom they love so profoundly that even the unknown anticipation of their grief can be felt beyond the bounds of a single reality. Of course, we are limited and parochial creatures in many ways, and truths cannot always displace our fears.
It is easy enough to understand how an imperfect understanding of namelings became the mistrust and paranoia around changelings, how the impenetrable motivations behind the actions of faeries lends the most well-intended mercies the air of something sinister; particularly when said mercies undermine the ways in which we define and delineate the self from even a flawless approximation of the same. Allowing for a brief of adjustment and reorientation, it takes perhaps a day for what was to be consumed in the consolidation of what it has become, they lose any strengths or weaknesses that their original forms would have conferred. No longer immortal - but no longer poisoned by the fact of being in this world - at this point nothing known to science or magic can divine anything but (or anything untoward about) their human mortality.
The most vital essence of changelings as a narrative abstraction of an unalloyed, unrecognised truth is that they were never - and could never really be - human. It speaks to a deeper issue around accepting our place in a universe vastly more complex and complicated than most people will ever know: The need to hold ourselves (and our selves) sacrosanct and apart, to be the rock on which the endless incoming tide of things we once believed to be impossible must break. It is our first and perhaps our final tragedy - if we cannot accept a certain plasticity within our fundamental values then we cannot exist alongside the miraculous any more than we can exist alongside the monstrous. Instead, fearing conquest, we will seek to conquer; and it will be the undoing we deserve.