I like the explanation Gordon Liddy gave for saying "thousand million" instead of "billion." He said billion was a number so big that people couldn't really grasp what it meant, but most people could envision a thousand dollars. If you spent a thousand dollars a day, it would take you roughly three years to spend a million dollars--or roughly three thousand years to spend a thousand million dollars at that same rate.To put those numbers in perspective; if we equate one dollar to one second then the following roughly applies.
One million seconds ago was about a week and a half ago.
One billion seconds ago was early 1982.
One trillion seconds ago was about 31,709 years ago.
Put another way, if you had a billion dollars and had started spending a thousand dollars a day on the day Jesus was born (ignoring your short lifespan and calendar shenanigans along the way), you'd still have roughly $300 million left. And I'm sure you'd have a lot more to show for it than does Uncle Sam...