Where do I start?
When I was very tiny, back when I still thought that every language had its own alphabet (how could it be otherwise?), my favorite bedtime story was Beowulf. Sometimes my father read it to me in Old English. Sometimes he read it to me in modern English from the Norton anthology. Sometimes he retold it out of his head using small words and directing my attention back to the original words when there was a link. Beowulf was important.
A few years ago I happened to see Seamus Heaney's translation of Beowulf at Third Place Books and picked it up mainly for the pictures. Once I got into it, I was intrigued by Heaney's description of how he found his register - he brought up in his mind's eye (or ear) the sound of some of his father's relatives and used their voices to achieve what he calls "forthright delivery."
I know that's something I do. I shamelessly use friends and relatives to choose a register for translating dialogue. If I've ever talked to you, consider this fair warning.
In a similar vein, a while back I read an interview with a Russian screenwriter who admitted that he researched the speech patterns for the cops in one of his movies by watching hours and hours of amateur videos posted online by young cops. Hats off to him for that, of course.
But back to Beowulf. The hero's name is a cypher for "bear" (bee+wolf). Interestingly, the Russian word for bear - медведь - is also a cypher: "one who knows where to find honey." Several people have told me that there used to be another word for bear in Russian: бер (ber). For whatever reason, Russians preferred to call the bear by a nickname and the nickname eventually outlived the true name. You can see the older word in the name for a bear's cave: берлога (ber-LO-ga, or "bear-lying place").