the experience of grendle in the original flashing between comprehensibility and jumbled letters is as far back as I have gone, but I read everything truely ancient that I can get my hands on from any culture in any language(translated) and try and make sense of it best as I can
I can comprehend most of the text back to 1300, if slower than Modern/Present Day English. It helps to know the old letter forms, and some of how Shakespearean (Early Modern), Middle, and Old English work. It also helps sounding it out.
Past that, I'm not familiar with Old English enough to understand and follow the text.
Knowing a bit of German or Dutch helps as well.
I posted my amateur translation of 1200 here: https://news.ycombinator.com/item?id=47102874
At first it stumped me, but I spent some time on it and it started to become intelligible. I didn't look up any words until after I was done, at which point I looked up "uuif" (woman/wife) since I wanted to know what manner of amazing creature had saved the protagonist :D
Knowing that W is a late addition to the alphabet and would have been written UU or VV suddenly makes uuif obvious.
I could intuit the pronunciation but I didn’t make the connection from “wif” to “woman” in general. In hindsight I should have, after all we have words like “midwife” which doesn’t refer to a person’s actual married partner.
"Wif" meant woman at the same time that "wer" meant man and "man" meant person.
Man changed to mean only a male person, and we lost wer except in the word "werewolf".
I’m a native English speaker and I think this is an easier jump if you know other Romance languages. In Spanish and Portuguese “woman” and “wife” are often the same word, “mujer” and “mulher” respectively.
Also French femme. It isn't limited to Italic languages either. There's also German Frau, Dutch vrouw, Irish bean.
Czech žena