Here's a little chart of words that we still understand. The older the word, the bigger it is: the newer, the smaller. If you click doubly on the picture you ought be able to see it more clearly.
The picture was drawn up by a chap called Mark Pagel at the University of Reading, for an exhibition at the Serpentine Gallery. The underlying principle is, of course, that the more basic a word is, the less it changes. Highfalutin words, like, for example, highfalutin, tend to be much more mutable. The most central words are as unchanging as a tramp's pants.
It is possible to write whole sentences that would have been understood in Anglo-Saxon times, more than a thousand years ago. For example:
Harold is swift. His hand is strong and his word is grim. Late in life he went to his wife in Rome.
However, most Anglo-Saxon sounds to modern ears like utter gobbledygook (a word that was not invented until 1944).
Lots more strange maps here.
The Inky Fool school for the study of ancient languages