This seems to be a popular etymology in feminist circles these days. Hag derives from the Greek hagia for holy. That is, a holy woman, a mystic, a bridge between heaven and earth. Just do a google search on [hag hagia] Like this “But [the hag] Cerridwen’s origins are pre-Celtic and the word “hag” is a derivative term of the Greek hagia which meant sacred or sanctuary. “
Interesting that the etymology that I would have confidence in is close, alas, no cigars.
etymonline has: shortening of the Old English hægtesse which may have cognates in the German Hexe and Dutch Heks for witch or fury. But then also a connection with hedge which may be a border between civilization and the wild world beyond (etymonline).
So this nice lady named Faith at theolog “What a great picture of this woman as a hag—from the word hagia, holy.”
I doubt it. But the bridge between the meanings is pretty tempting. Still, folk etymology to be sure.