The word "bus" is a contraction of "omnibus", a form of the Latin word "omnes" meaning "all" or "everyone". It appeared in Paris in 1819–20 as "(voiture) omnibus" meaning "(carriage) for all", See https://en.wikipedia.org/wiki/Bus#Etymology

You don't often hear the full form "omnibus" these days. But here is a nice little song about the famous London double-decker omnibus:

https://www.youtube.com/watch?v=mVHbF0jAzMw

More Info: en.wikipedia.org