Source: TW
Trollaukin: further insight into berserkrgangr. As late as the 19th century, a practice that was forbidden in Icelandic wrestling (Glíma) was trollaukin; a term meaning “possession by trolls/spirits”, with the intent of gaining increased strength and fighting ability.
According to Jón Árnason, an invocation would be said, such as “Stand by me, my troll!”, or “Stand by me fiend/troll, now possessing me!”. By this time, “troll” had become a blanket term for all manner of supernatural entities, especially those who aided in sorcery.
Because the fylgja doesn’t fit with the Christian conception of the soul, fylgjur may very well have been categorized as “trolls.” Árnason’s account could fit with Lotte Hedeager’s theory about berserkrgangr being, in essence, a practice where a warrior would allow his fylgja to take over, to possess him. Before Iceland’s formal conversion, such berserkr prayers may have sounded like;
“Standa með mér, mínn fylgja!”
“Standa með mér fylgja, hafa mig nú!” ᛉ