I can read back to 1500, but 1400 reads like a different language. To be fair this quite remarkable, given:

> Before the mid 1700s, there was no such thing as standardized spelling.

It felt like it was become more Germanic, and that appears true:

> The farther back you go, the more the familiar Latinate layer of English is stripped away, revealing the Germanic core underneath: a language that looks to modern eyes more like German or Icelandic than anything we’d call English.