I assume most of you reading this are English speakers (native or otherwise), and as such you are probably aware of how much one language can vary between geographical areas. We have a huge variety of accents, dialects and regional words and phrases that fall under the general banner of "English".
George Bernard Shaw once even observed that "England and America are two countries separated by a common language".
Imagine what would happen if you were able to travel back in time, perhaps hundreds of years back and listen to English speakers then? You probably think you have a pretty good idea of how some English words have changed, and might expect more "thee's" and "thou's" to pepper peoples' speech in those earlier times.
If you went back far enough, though, things might get very odd indeed...