Flyting

Language warning, although it's 500 years old.

The five sections to the compilation are devoted to religious themes, moral or philosophical themes, love ballads, fables and allegories, and comedy, especially satire. The latter section is where one is most likely to encounter the swears, particularly in the poetry of William Dunbar and Walter Kennedy. Both poets feature in the poem where the notorious F-word appears: "The Flyting of Dunbar and Kennedie."

Flyting is a poetic genre in Scotland—essentially a poetry slam or rap battle, in which participants exchange creative insults with as much verbal pyrotechnics (doubling and tripling of rhymes, lots of alliteration) as they can muster. (It's a safe bet at this art form.)

Dunbar and Kennedy supposedly faced off for a flyting in the court of James IV of Scotland around 1500, and their exchange was set down for posterity in Bannatyne's manuscript. In the poem, Dunbar makes fun of Kennedy's Highland dialect, for instance, as well as his personal appearance, and he suggests his opponent enjoys sexual intercourse with horses. Kennedy retaliates with attacks on Dunbar's diminutive stature and lack of bowel control, suggesting his rival gets his inspiration from drinking "frogspawn" from the waters of a rural pond. You get the idea.

Flyting is not just "a poetic genre in Scotland," but in fact also Old Norse. Several of the surviving stories about the Norse gods involve them mocking each other in this way, especially Lokasenna (Loki actually did have sex with a horse) and Hárbarðsljóð (in which Odin mocks Thor while in disguise as a boatman).