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1610s, "deputy governor in Mogul Empire," Anglo-Indian, from Hindi nabab, from Arabic nuwwab, honorific plural of na'ib "viceroy, deputy," from base n-w-b "to take someone's place." Also used of Europeans who came home from India having made a fortune there, hence "very rich man" (1764).
deputy ruler, or viceroy, under the Mughal rule of India. The title was later adopted by the independent rulers of Bengal, Oudh, and Arcot.