The Finnish and Karelian word runo [‘poem’] has been viewed as
reflecting a loan from Proto-Germanic *rūnō, the ancestor of Old Norse
rún [‘rune’]. However, given its limited distribution in Finnic and the
meanings attested in Germanic and Finnic languages, the word was more
likely borrowed at a later stage, from Early Norse near the start of the
Viking Age, probably in the meaning of ‘incantation, verbal charm’ and
in connection with incantational magic.