Becca & InfoMarex

Etimologia
Late 14c., from Anglo-Norm. brocour "small trader," from Anglo-Fr. abrokur "retailer of wine, tapster," perhaps Port. alborcar "barter," but more likely O.Fr. brocheor, from brochier "to broach, tap, pierce (a keg)," from broche "pointed tool" (see broach (n.)), giving original sense of "wine dealer," hence "retailer, middleman, agent." In M.E., used contemptuously of peddlers and pimps.
http://www.etymonline.com/index.php?term=broker

Definizione
A person whose business is to negotiate buying and selling, esp. of stocks, on another's behalf.
http://www.wordsmyth.net/live/home.php?script=search&matchent=broker&matchtype=exact

BROKER (according to the New English Dictionary, from Lat. brocca, spit, spike, broccare, to " broach " - another Eng. form of the same word; hence O. Fr. vendre a broche, to retail, e.g. wine, from the tap, and thus the general sense of dealing; see also for a discussion of the etymology and early history of the use of the word, J. R. Dos Passos, Law of Stockbrokers, chap. i., New York, 1905). In the primary sense of the word, a broker is a mercantile agent, of the class known as general agents, whose office is to bring together intending buyers and sellers and make a contract between them, for a remuneration called brokerage or commission; e.g. cotton brokers, wool brokers or produce brokers. Originally the only contracts negotiated by brokers were for the sale or purchase of commodities; but the word in its present use includes other classes of mercantile agents, such as stockbrokers, insurance-brokers, ship-brokers or bill-brokers. Pawnbrokers are not brokers in any proper sense of the word; they deal as principals and do not act as agents. In discussing the chief questions of modern legal interest in connexion with brokers, we shall deal with them, firstly, in the original sense of agents for the purchase and sale of goods.
http://encyclopedia.jrank.org/BRI_BUN/BROKER_according_to_the_New_Eng.html

Voce ingl.; propr. 'mediatore'
Vedi
Sinonimi e Contrari
Definizione
s. m. invar. (fin.) intermediario d'affari che compra o vende titoli, merci e servizi su commissione, percependo una percentuale sull'ammontare dell'operazione | consulente nel settore assicurativo.
http://www.garzantilinguistica.it/it/dizionario/it/lemma/1ff21da90fe9fccf6039dd6df69123f7cf660b65

Traducente
broker [n] intermediario; mediatore; broker o (codeluppi) mantiene la caratteristica distintiva di operare per conto proprio.

Intermediario finanziari che nell'industria dei servizi di investimento opera sul lato dell'offerta per conto della clientela. I broker pongono in essere le negoziazioni che il committente intende effettuare mediante la ricerca di altri oggetti disposti a negoziare a condizioni compatibili. Il broker è un fornitore di accesso al mercato.
http://www.borsaitaliana.it/bitApp/glossary.bit?target=GlossaryDetail&word=Broker