GRIM
European Mythology
A type of Spirit
This is an ancient European SPIRIT of the night. Originally an alternative name for one of the aspects of ODIN, it was later applied to the goblin or demon assuming a terrifying form, usually that of a large black dog or an owl, whose wails beneath the windows of the sick predicted their demise. This aspect of the FAIRY GRIM is described in The Life of Robin Goodfellow (1628). Different aspects of the SPIRIT'S role are denoted by a prefix, as in the FOSSEGRIM of Norway and the KYRKOGRIM, KIRKEGRIM, and CHURCHGRIM of Sweden, Denmark, and England, respectively. Essentially the GRIM is a warning rather then a terrifying SPIRIT.
SOURCE: Spirits, Fairies, Leprechauns, and Goblins: An Encyclopedia