The story of the Duel of Samso was preserved along with other ancient Norse poems in the Codex Regius (AKA The Royal Book.) It’s original creation and writer is lost to time, but it was found in the possession of an Icelandic Bishop, Brynjolfur Sveinsson (Do Icelanders know how to name folks or what? He’s on Icelandic money, he’s so bad ass.) The legends contained in the Codex Regius pre-dated Christianity, also J.R.R. Tolkien was a massive fan boy for it and it permeates throughout all his work. (What’s more impressive?)
Unlike The Odyssey, no single author is attributed to the Codex Regius or the Tyrfing Cycle. They were minstrel poems, told by a seafaring, far traveling people. They were malleable and adapted to the audience. Your characters’ deeds and adventures, became their heroes’ deeds and adventures. Your stories, became their legends. They were the first crossovers. Who wouldn’t want to watch a flick where John McClane and Martin Riggs tussle? The crossover aspect is what most appealed to me.
Why are all these Norse legends in Iceland, you ask? Isolation and Christianity was straight lazy, “Pfft… Iceland? Way over there. Why bother?” So the old stories were still told, passed along and remembered.
My primary reference (besides the magic of the internet, don't go quoting me in some term paper, all hail Wikipedia!) was the Poetic Edda, a modern collection of these poems. Is this all confusing? Damn straight. With so many retellings and translations, things get lost in the sauce. Tyrfing is found primarily in the Hervarar Saga (but also in Orvar-Odd’s Saga, crossover!) Since, each of these stories are a amalgamation, variations of the characters appear in multiple histories and legends, it all gets jumbled up, a mashup.