1832, abbreviation of omnibus (q.v.). The modern English noun is nothing but a Latin dative plural ending. To miss the bus, in the figurative sense of "lose an opportunity," is from 1901, Australian English (OED has a figurative miss the omnibus from 1886). Busman's holiday "leisure time spent doing what one does for a living" (1893) is probably a reference to London bus drivers riding the buses on their days off.
To clear dirty dishes and tableware from the tables in a restaurant or cafeteria (1913+)
[the restaurant sense probably fr the four-wheeled cart often used to carry dishes]