Anyone who's ever taken a high school English literature course knows that if you go back far enough, English gets real cray. The high diction of the 1800s might take a few rereadings to help piece together, but it's still close enough to our lexicon that you can get the general gist of what people are saying. And Shakespeare is fairly comprehensible once you get past the weird pronunciation. But if you go back to Middle English, like The Canterbury Tales, woof. You can't tell a love poem from a cooking recipe from a weather forecast. 

Don't know what crapulous, hugger-mugger, petty fogger, mumpsimu, bleater, or batty fang mean? You will soon enough.