The Bogey-man was a devil derived from the Slavic bog, “god.” English cognates were bugabow, bugaboo, bugbear and boggle-bo which used to designate the pagan image carried in a procession to the May Day games. (see Maypole) “Humbug” came from the Norse hum, “night,” plus bog or bogey, i. e., a night spirit. The word “bug,” from the Welsh bwg, “spirit,” was applied to insects because of the old belief that insects were souls in search of rebirth. A mantis was a soul of the seer or wizard. A butterfly was Psyche, or a Female Soul.

Other derivations of bog were Scotish bogle, Yorkshire boggart, English Pug, Pouke and Puck; Icelandic Puki; the Puk of Friesland; the German Putz or Butz; Irisk Pooka and Welsh Pwcca; Danish Spoge and Swedish Spoka with theirEnglish offshoot of “spook.” The old English puca, a fairy, was applied to the old gods of Beltain. So Puck was the same as the witches’ god Robin. A.G.H.

Source: 56.