Victor Dewsbery has added a post in his blog Language Mystery going into great (and alas necessary) detail on millions, milliards, billions, trillions etc.
This history of the number systems has also created “false friends” for translators. A German “Billion” is not the same as an English “billion”. The words “Trillion” and “Quadrillion” are also misleading. And a German “Milliarde” is not a “milliard”.
This much I remember, and I am very grateful to Victor for setting it out so well. Take a look around for other topics while you’re there.