I learnt somewhere that English is a essentially hotchpotch of different languages and a lot of words are from French (it has something to do with the Norman Conquest...). Actually, I do find learning French helps boost my English vocabulary a lot.

So, is the above formula true? Of course, there are words from other languages as well but mainly the above three?

Is there any good books that can tell me more about this? I need some citations badly.