Joan the wad is a Will-o'-the-Wisp in Cornish folklore and sometimes referred to as 'The Queen of the Piskies' and the consort of Jack o' Lantern.
‘wad’ is a dialect word for a torch.
Originally limited to the area round Polperro, where it was noted by Jonathan Crouch in his history of the town.
Piskies particularly loved to lead people astray, often into bogs and marshes, by appearing like the light from a cottage window or as a man carrying a lantern. This was known as being 'Pisky-led' and explains another name for the Pisky - Jack o' Lantern. It is commemorated in the rhyme:
- Jack o'the lantern! Joan the wad,
- Who tickled the maid and made her mad!
- Light me home, the weather's bad
In other collections of Cornish stories, she actually is the Jack o' Lantern. It is considered lucky to carry a small carving or image of her, hence the rhyme.