philomaela:

The sagas were born in a cultural ferment where laws, genealogies, navigational details, historical events, origin myths, family stories, folktales, and poems were transmitted by word of mouth. They began life as oral stories, reshaped and retold as they were passed down the generations, moulded by the many mouths, elaborated to incorporate new details and embellished to make better winter tales to tell around the fireside.
~Eleanor Rosamund Barraclough, Beyond the Northlands: Viking Voyages and the Old Norse Sagas