Makes sense. I did an experiment some months ago. To really get this, you have to be able to read both French and English.
Here is a text of Beowulf, an epic poem in Old English written sometime between the 8th and 11th centuries -- probably somewhere in the 900s.
http://catterall.net/OE/texts/a4.1.html
Here is a text of La Chanson de Roland, an epic poem in Old French written in the 12th century:
http://www.hs-augsburg.de/~harsch/ga.../rol_ch01.html
Roland isn't much later than Beowulf. Yet I can (sort of) read Roland, or at least it's quite recognizable as being French. Beowulf? Almost pure gibberish. You have to be an Old English scholar to read that thing. Old English is a foreign language to modern English speakers.
Here's something that is to modern English very much as Roland is to modern French:
http://www.librarius.com/cantales.htm
(Click on any of the chapter links on the left frame.)
This is Chaucer's Canterbury Tales. It was written probably about three hundred years after Beowulf. The language is called "Middle English," but although it's archaic, it's easily recognizable as English. More than twice as much time has elapsed since it was written than passed between Beowulf and Chaucer's time. Yet English has changed far less in those 600+ years than it did between the 10th and 14th centuries. It's changed, yes, but it's recognizably the same language, just as modern French and the language of Roland are recognizably the same language, although changed.
The Norman conquest totally transformed the language. So it's not at all surprising how much French vocabulary has become part of modern English.