Spriggans from nearby Bartinney Downs substitute a child with one of their own? Or just plain child abuse. Make your mind up with the song at sacred-texts.com/neu/eng/prwe/prwe033.htm
Hunt’s ‘Popular Romances of the West of England’ (1886).
Here’s an extract that mentions the ritual at the well which Janey attempts to get rid of the changeling.
On the three first Wednesdays in flow’ry May
She plunged it deep at the dawn of day--
Pass’d it slowly three times against the sun,
Went three times round,--and when all was clone,
The imp of a child roar’d aloud for fun.
No tongue can tell
The trouble it gave her
To dip the shaver,
And work the spell.