For example, "centipede" nominally means 100 feet, though https://en.wikipedia.org/wiki/Centipede says "Despite the name, no centipede has exactly 100 pairs of legs; number of legs ranges from 15 pairs to 191 pairs, always an odd number."

Centibillionaire is the obvious extension of centimillionaire, and "centimillionaire" has been around for a long time. https://archive.org/details/per_chicago-daily-tribune_the-ch... shows a use in 1883, explicitly referencing $100,000,000 of Vanderbilt capital.

(A Google Books search finds two other uses of centimillionaire in the 1800s.)

Another old word using centi- to mean 100 is "centimillennium", for 100 thousand years. Here is an 1882 use: https://archive.org/details/loverinschartoft00love/page/36/m... and Wiktionary adds several more recent uses at https://en.wiktionary.org/wiki/centimillennium .

I thought of this idea when I was 14 and immediately dismissed it- long before this guy came along and claimed it was such a "great idea." Why did I dismiss it?

Terrorism. In the best case, all you'd need to do is punch a hole in the side of the tubes, and any train would hit a wall of air at supersonic speeds. In the worst case, it would derail catastrophically when it hit my hole if it were big enough.

It's a terrible idea for so many reasons.