Gwyllion or gwyllon (plural noun from the singular Gwyll or (Yr) Wyll "twilight, gloaming") is a Welsh word with a wide range of possible meanings including "ghosts, spirits" and "night-wanderers (human or supernatural) up to no good, outlaws of the wild." Gwyllion is only one of a number of words with these or similar meanings in Welsh. It is a comparatively recent word coined inadvertently in the seventeenth century by the Welsh lexicographer Dr John Davies of Mallwyd.[1]