A member of the fairy tribe similar to a hob, hobthrust, hobgoblin or brownie. They tend to inhabit isolated farmhouses in Northern England, and have done since Tyme Immemorial. Of a helpful nature, they'll do all kinds of housework, but are inclined to play pranks if not given their customary bowl of milk. Nowadays, their misbehaviour is ascribed to poltergeists. If offered clothes they will leave for good.
It is also spelt 'chimaera' reflecting its Greek origin. Originally, it was a fabulous beast - a fire-sputing monster with a lion's head, srpent's tail and a goat's body. It came to mean any idle or wild fancy, especially one that would prove to be short-lived, to 'melt away' like a mirage.
Nowadays, this word is very commonly used to refer to the socks often worn by schoolgirls, usually in white, either ankle or knee-length. I wore them myself until I was at least 14. Pelerine socks always have a patterned weave, rather than plain or ribbed. Pelerine is not a trade name, and I've no idea how it came to be applied to these particular socks. The term arrived in England in the 1980s, probably from France. I doubt whether pilgrims ever wore them!