What does "therf werre eyght bokes" mean?
"Therf werre eyght bokes" isn't a grammatically correct sentence.
It's used as an example on a number of websites and books to show that having a really large spell-checker dictionary isn't necessarily a good thing because if your spell-checker contained every word in the Oxford English Dictionary then "Therf werre eyght bokes" would be shown as correct.
The sentence looks similar to "There were eight books", but the original is a deliberate example of an incorrect or nonsense sentence.