Certain Je Ne Sais Quoi

English as we know it today is enriched with many borrowings and influences from other languages. Aficionado, chutzpah, pro bono, hoi polloi, ketchup, nous, zeitgeist - we use these foreign words every day without thinking of their origins, but what do they actually mean? And just how and why did we English speakers absorb such exotic imports? Each phrase has a fascinating history; colonialism, fo...