What does septillion have to do with seven?

Answer 1

In the old system used in the UK, a billion was a million million, a trillion was a million billion or a million million million and so a septillion was a million million million million million million million or million7. So septillion DID have something to do with seven. However, this system left large gaps in the names of numbers which were of increasing importance in every day life eg GDP, world population. The US system, which used billion = thousand million, trillion = thousand billion or thousand thousand million was adopted by most countries as more practical - even if it meant that the names no longer meant what they seemed to mean. In general, nowadays, an n-illion = (thousand)n+1 . Not very memorable, but that's the best I can do.