I hadn't even thought about that. I just looked at Wikipedia and Chaucer's Canterbury Tales are from the late 1300's. In the show they explicitly mentioned the language was associated with works like that. So yeah, if the kid was from 1590, that's 1-2 hundred years too late. Wikipedia says "Middle English describes dialects of English in the history of the English language between the High and Late Middle Ages, or roughly during the three centuries between the late 12th and the late 15th century." 1590 is the late 16th century. Oops.
Nonetheless I still enjoyed the episode. But that does seem unusually sloppy for a show that's trying to establish its own history. It wouldn't have been too hard to just say "early modern English" instead, would it?
If he had spoken "early modern English" they wouldn't have needed Ichabod to translate. Ever read, or listened, to Shakespeare? That's roughly the type of language the boy should be using. Possibly they'd need a bit of help here and there.
One aside: did anyone actually listen to the words they said when speaking Middle English? Some of it was quite recognizable (making the subtitles unnecessary), but some of it I would have been confused had they not labeled it. I thought that was well done (even if it was the wrong language as pointed out).
It made me think of Brad Pitt's character in Snatch: even the subtitles couldn't figure out what he was saying:
I thought they did a pretty good job with the actual language. I can vaguely recall reading Chaucer's tales in the original langue in both high school English and again in college, and with some struggling I could at least get the gist of whats being said. Spoken language would probably be tougher. Very different from old English (ie Beowulf), that may as well be Greek.
I always thought Brad Pitt in Snatch was doing an obviously comically exaggerated Romani/Gypsy accent. I don't think I could catch a word.