exchange:  Like change, exchange comes ultimately from Latin cambīre ‘barter’. In postclassical times this had the prefix ex- added to it, here functioning as an indicator of ‘change’, producing late Latin *excambiāre. In Old French this became eschangier (whence modern French échanger), which English acquired via Anglo- Norman eschaunge. A 15th-century reversion to the original Latin spelling of the prefix produced modern English exchange. => change
late 14c., "act of reciprocal giving and receiving," from Anglo-French eschaunge, Old French eschange (Modern French échange), from Late Latin excambium, from excambiare, from Latin ex- "out" (see ex-) + cambire "barter" (see change (v.)). Practice of merchants or lenders meeting to exchange bills of debt led to meaning "building for mercantile business" (1580s).