mid-14c. (mid-13c. in surnames), "commercial agent, factor," also "an agent in sordid business," from Anglo-French brocour "small trader," from abrokur "retailer of wine, tapster;" perhaps from Portuguese alborcar "barter," but more likely from Old French brocheor, from brochier "to broach, tap, pierce (a keg)," from broche (Old North French broke, broque) "pointed tool" (see broach (n.)), with an original sense of "wine dealer," hence "retailer, middleman, agent." In Middle English, used contemptuously of peddlers and pimps, "one who buys and sells public office" (late 14c. in Anglo-French), "intermediary in love or marriage" (late 14c.).
"to act as a broker," 1630s (implied in brokering), from broker (n.). Related: Brokered.
"action of making (something) to a customer's specifications," 1975, noun of action from customize (v.).