1911 Encyclopædia Britannica/Hag
HAG. (1) (Probably a shortened form of the O. Eng. hægtesse, hegtes, cognate with Ger. Hexe, witch, Dutch hecse), a word common during the 16th and 17th centuries for a female demon or evil spirit, and so particularly applied to such supernatural beings as the harpies and fairies of classical mythology, and also to witches. In modern usage the word is generally used of a hideous old woman whose repulsive exterior is accompanied by malice or wickedness. The name is also used of an eel-like parasitic fish, Myxine glutinosa, allied to the lamprey.
(2) A word common in Scottish and northern English dialects for an enclosed piece of wood, a copse. This is the same word as “hedge” (see Hedges) and “haw.” “Hag” also means “to cut,” and is used in Scotland of an extent of woodland marked out for felling, and of a quantity of felled wood. This word is also used of a cutting in the peat of a “moss” or “bog,” and hence applied to the small plots of firm ground or heather in a bog; it is common in the form “moss-hags.”