borrowed from Latin negōtiātus, past participle of negōtiārī "to do business, trade, deal," derivative of negōtium "work, business, difficulty, annoyance," from nec "not" + ōtium "free time, leisure, tranquility," of obscure origin — more at neglect entry 1

Note: The sense "to confer in order to arrive at a settlement" is probably based on Middle French negocier or Italian negoziare, which had developed this sense, not belonging to the Latin source, by the mid-16th century.

circa 1598, in the meaning defined at intransitive sense