Margaret Ann Courtney defines the pisky as people who aren't bad enough for Hell and not good enough for Heaven:

These small people are said to have been half–witted people who had committed no mortal sin, but who, when they died, were not good enough to go to heaven. They are always thought, in some state, to have lived before.

The small people go about in parties, but the pisky in his habits, at least in West Cornwall, is a solitary being. I gather, however, from Mr T. Q. Couch's History of Polperro that in the eastern part of the country the name of Pisky is applied indiscriminately to both tribes. He says two only of them are known by name, and quotes the following rhyme:

Jack o' lantern! Joan the wad,
Who tickled the maid and made her mad;
Light me home, the weather's bad.

Here in the west he is a ragged merry little fellow (to laugh like a pisky is a common Cornish similie), interesting himself in human affairs, threshing the farmer's corn at nights, or doing other work, and pinching maidservants when they leave the house dirty at bed–time.

Joan the Wad, what could that possibly mean? A look in our glossary will tell you that a wad is an ignis fatuus, a light seen over marshes that is believed to lead people astray. It is commonly called will–o'–the–wisp (Will for William).

A wisp is a twist of straw burning as a torch. A wisp is also called a wad. A will–o'–the–wisp is also called a Jack–O'–Lantern: a personification of the light as Jack and his lantern. Personification names include Will, Jack, Joan, Gill, and Robin.