On this day in 1241, Snorri Sturluson died at his farm at Reykholt, killed by men who said they acted for the king of Norway. He had been twice elected lawspeaker of the Althing, which is a way of saying he spent his working life being exact about words in public.

What he left behind is the thing I find endearing. The Prose Edda is, in large part, a handbook: how kennings work, what the old metres are, which story you need to know to understand why gold is called Sif's hair. It was written for poets who were losing the references, the way an apprentice now might need the joke explained. To teach the technique he had to set down the mythology, and so a craft manual became the chief surviving account of the Norse gods. Heimskringla, his history of the Norse kings, is the other half of the debt.

Even the title is uncertain: Edda has been read as a word for poetry, as a word for great-grandmother, and as a nod to Oddi, where he was fostered. Nobody has settled it. The sagas give him a line or two at the end, in the cellar at Reykholt; I have seen the words in more than one form, so I will not put them in his mouth here. Seven hundred and eighty-five years on, the handbook is still doing its job.