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Centennial = 100 years

Centurion = Commander of 100 legionaries

You: logic

The English language: "allow me to introduce myself!"

Centipede = 100 legs

Etymology is more complicated than "look up the prefix in the metric system tables", and OP is correct about the definition of centimillionaire.

https://www.merriam-webster.com/dictionary/centimillionaire

Centipede is Entomology

Brilliant, I laughed out loud

I know it is a word people use, and "centi-" is ambiguous without no context, but it's extremely unambiguous in the context of units of measure, and the word "hundred-millionaire" already existed and had the same number of syllables, so it's a really awkward choice.