Will o' the Wisp

... First of all, monsters were created as strange personifications of the forces of nature that were the object of worship for ancient people. Examples include Cailleach Bheur (a symbol of winter), an evil witch who lurks in the Scottish mountains and freezes the ground and lakes by touching them with her walking stick; Jack Frost (a personification of frost), an Englishman who laughs and spreads cold, causing people to freeze to death; Will o' the Wisp (a personification of fire), a will-o'-the-wisp who never finds rest; and Portune (a personification of farmland), a wrinkled-faced dwarf who constantly tills the soil and roasts and eats frogs when he rests. There are also many examples of monsters that take the form of animals, and the nature and characteristics of the animal they are modeled after are usually reflected in the monsters themselves.

*Some of the terminology that refers to "Will o' the Wisp" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…　妖怪はまず，古代人の信仰の対象であった自然力の奇怪な擬人化として成立する。スコットランドの山中に潜み，地面や湖面を杖で触れて凍らせる妖婆カリヤク･バルCailleach Bheur(冬の象徴)，笑い声をあげて寒気をふりまき人を凍死させるイギリスのジャック･フロストJack Frost(霜の擬化)，安息を得られぬ鬼火とされるウィル･オ･ザ･ウィスプWill o’ the Wisp(火の擬人化)，土を耕しつづけ休息時にカエルをあぶって食べる皺だらけの顔の小人ポーチュンPortune(農地の擬人化)などがこれである。また動物の姿をとる妖怪の例も多く，通常はモデルにされた動物の性質や特徴がその妖怪にも反映される。…

※「ウィル・オ・ザ・ウィスプ」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報