Senna (poetic)
Senna is a form of Eddic poetry consisting of an exchange of insults between participants, ranging from the use of expletives to accusing an opponent of moral or sexual impropriety. It traditionally existed in an oral form, with the famous skald Þórarinn Stuttfeldr once describing the poetry of his opponent as being like leirr ens gamla ara or 'the mud of the eagle'; literally claiming that his poetry was like dung.
There are also numerous written examples of senna in Old Norse-Icelandic literature, including the Ölkofra Þáttr (The Tale of the Ale-Hood) in which a carpenter is accused of setting fire to the wood of six powerful chieftains while burning charcoal, and the eddic poem Lokasenna, which consists of a duel of words between Loki and several other Norse gods, and in which Loki accuses the other gods of sexual misdeeds.
References
"Serial Defamation in Two Medieval Tales: The Icelandic Ölkofra Þáttr and the Irish Scéla Mucce Meic Dathó". Oral Tradition 6/1: 35–57. 1991.
"Performance and Norse Poetry: The Hydromel of Praise and the Effluvia of Scorn". Oral Tradition 16/1: 168–202. 2001.
"The Senna: from Description to Literary Theory". Michigan Germanic Studies. 1979.