Is it ensure, insure, or assure?
"stock exchange," 1570s, burse, from Old French borse "money bag, purse" (12c.), from Medieval Latin bursa "a bag" (see purse (n.)). French spelling and modern sense of "exchange for merchants" is first recorded 1845, from the name of the Paris stock exchange. The term originated because in 13c. Bruges the sign of a purse (or perhaps three purses), hung on the front of the house where merchants met.