From pidgin English, from a Chinese Pidgin English pronunciation of English business during trade in the Far East.
All attestations of pidgin from the first half of the nineteenth century given in the third edition of the Oxford English Dictionary mean “business; an action, occupation, or affair” (the earliest being from 1807).
Other suggested derivations include:
Hebrew פִּדְיוֹן
Chinese pronunciation of Portuguese ocupação ("occupation; business")