It vividly recalls the use of the same epithet in the name The Seven Haley Isles, a seamen's noa term for the Flannan Islands (SGS, xi, 88). A further striking parallel is offered by Eng. halibut lit. 'holy butt' and its many Germanic cognates, terms which certainly arose in a milieu conditioned by intense superstition[…]
Source: wiktionary
The power of the spoken word has meant that some dangerous things are not mentioned by their "real" names, but by noa terms, like gullfot (literally "golden foot") for "wolf", or tallbjörn (literally "pine bear"), granoxe (literally: "fir ox"), trädräv (literally: "tree fox") or granälg (literally: "fir elk") for "squirrel".
Source: wiktionary
Blå Jungfrun […] is a noa name. The tabooed name of this island is Blåkulla, Blue Hill (or Rock), a recurring name of the home of the witches in the North.
Source: wiktionary