Frigg

Frigga is a Norse Goddess mentioned occasionally in the How to Train Your Dragon Franchise.

Friday is named after "Frige's Day".

Mythology
There is some evidence that Frigga and Freya originated from the same deity, but later became separate entities. Frigga is known to many Germanic pre-Christian cultures, whereas Freya is not known well beyond Norse Mythology. Frigga is the wife of Odin and the mother of Baldr. She also asked all the plants from which weapons were made for oaths not to kill her son, all except Mistletoe. No weapons hurt him, but the God Loki hears of mistletoe and arranges for Baldr to be shot with an arrow of mistletoe.

Dragons: Riders of Berk Comics
In the comic "The Legend of Ragnarok", Savage utters Frigga's name when Alvin presses his men to sail onward across dangerous seas to Berk.

Dragons: Race to the Edge, Season 2
The Island of Friga is introduced as a wedding site for the Hooligans in "Snotlout Gets the Axe".

Dragons: Rise of Berk
One of the locations searchable by Toothless includes an island called Frigg's Hearth.

The Isle of Friga also appears as a searchable location in this game.