Manx 'malart' / Irish 'malartú' (the swap, the exchange) + Irish '-ín' diminutive — the little swap
She was left in place of a healthy boy, and the family loves her while the mother cannot stop noticing her eyes do not move the way a child's eyes should.
Best for A fairy-child substitute in a cradle
Scottish Gaelic 'atharrachadh' (change, the change of) + '-ach' (the one of) — the changed-one
He was a fat, laughing baby for a month and then grew thin and old-faced overnight, and the midwife crossed herself and would not return to the house.
Best for A swapped infant who is not what it seems
Scottish Gaelic 'fosgailte' (open, as the hill opens) reshaped — the hill-opened
He remembers the green door of the hill opening and a hand taking his own, and remembers nothing else of the human house he was born in.
Best for A changeling of the sídhe's open door
Sound-variant of 'fosgailte' (open) + harder ending — the one who came through the open hill
He grew up under the hill and was sent back to the human world as a young man, and he finds the food of mortals tastes of nothing and the sunlight burns.
Best for An adult changeling who knows the hill
Scottish Gaelic 'atharraich' (to change, imperative of change) reshaped as a name — the changed
She has lived ninety human years in nine fairy ones, and the family that lost her as a baby would now be older than the face she wears.
Best for A changeling grown to adulthood under the hill
Irish 'féith' (sinew, the hidden thread) + soft fairy-ending — the hidden-thread
She appears at the door of the dying in the shape of the one soon to die, and those who see her know to begin their mourning.
Best for A fetch, the double sent ahead of a death
Irish 'seachrán' (the wandering, the going astray) + fairy-ending — the gone-astray
He followed a light into the wood at the age of four and came back unchanged at the age of forty, wearing the same small coat.
Best for A changeling who wandered off and was taken
Scottish Gaelic 'corrach' (odd, strange, the queer one) — the strange one
He is thin and dark-faced and old-eyed, and the family cannot understand why their golden boy has become this, but he laughs at riddles no one else in the village can answer.
Best for An ugly old fairy passed off as a child
Scottish Gaelic 'creach' (the plunder, the spoil) — the plundered
She does nothing cruel, but the milk sours in the pail and the cow goes dry and the father's luck turns, and the family knows it began the night she came.
Best for A fairy whose presence is the family's plunder
Irish 'faol' (wolf, the wild outside) + reshaped fairy-ending — the wild-thing
She was found in the wood at three years old, speaking a language no one knew, and the family that took her in has never quite been sure whether the child they lost is the child they found.
Best for A feral fairy-child of the wood-edge
Irish 'caoith' (the shape, the form, reshaped from 'cruth') + '-ín' diminutive — the little shape
Her face is the dead image of the child she replaced, except in the corner of the eye, where it is briefly someone older.
Best for A fairy-child of an assumed shape
Irish 'aistriú' (to transfer, to move across) reshaped + fairy-ending — the transferred-one
He remembers two mothers, one with warm hands and one with cold bright eyes, and he is no longer certain which one he is supposed to call his own.
Best for A changeling moved between worlds