This is somewhat topical in that this year we should be celebrating the 180th birthday of the bus!
The odd history of omnibus
It started out in French in 1828 in its full form omnibus as part of the name for a new type of public transport that was open to everyone, of any social class. It was a long coach with seats down each side, which was called a voiture omnibus, a “carriage for everyone”, where omnibus is the dative plural of the Latin omnis, “all”, hence “for all”. (That classic Shakespearean stage direction, exeunt omnes, or “everybody leaves”, includes another form of the same word.)
The idea, and the word, were brought over almost immediately into England and into English. A London newsletter of 1829 noted that “The new vehicle, called the omnibus, commenced running this morning [4 July] from Paddington to the City”. As this shows, the French phrase was at once shortened (voiture was obviously foreign rubbish, but omnibus was classical and we could live with that). By 1832, it had been abbreviated further to the form we have today, bus, one of our weirder linguistic inventions, since it consists just of part of a Latin suffix, –ibus, with no root word in it at all. So immediate was the acceptance of omnibus into our language armoury that in 1831, only two years after its first use in English, Washington Irving could aim and fire it figuratively in reference to the Reform Bill: “The great reform omnibus moves but slowly”. World Wide Word, better than a thesaurus or dictionary