rune

riimu A letter, or character, belonging to the written language of various ancient Germanic peoples, especially the Scandinavians and the Anglo-Saxons.
A Finnish or Scandinavian epic poem, or a division of one, especially a division of the Kalevala.
A letter or mark used as mystical or magic symbol.
A verse or song, especially one with mystical or mysterious overtones; a spell or an incantation.
1891, Mary Noailles Murfree, In the "Stranger Peoples" Country'', Nebraska 2005, page 15:

the fiddle sang and sang as ceaselessly as the chanting cicada without, and the frogs intoning their sylvan runes by the waterside.