Oh no, you beat me to it 
Here was a thread from another forum where people found some pretty interesting Tiffany Problem examples 
I love that source I also recommend checking out Google Ngrams, which lets you search words and phrases, and can give an idea of how common a word or phrase was at a particular time. For example…
(Granted, this only shows you frequency in published works, which will on average tend to be more formal than how people would’ve been speaking 
)
Hwæt! We Gardena in geardagum, þeodcyninga, þrym gefrunon, hu ða æþelingas ellen fremedon
Yeah, it’s really interesting how having languages that “feels right” works for historical of more than a few centuries ago or that wasn’t even English-speaking in the first place—like something set in Ancient Rome, say, modern slang isn’t any more inaccurate than more formal English because they’re speaking Latin (or other ancient languages) anyway… but it still gives that impression. Happens with fantasy too; you realize everything is, in theory, in translation anyway, but you still have to pick what tone to set