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, foreign trade, invasion and immigration all have their role to play in the evolution of our language. Did you know, for example, that 'lingua franca' is Italian for 'Frankish language' – a name given to a mixed common language used by diplomats of different nationalities in medieval times? Or that the seemingly modern 'bandana' comes from the Sanskrit for the ancient Indian technique of tie-dying fabric? A Certain Je Ne Sais Quoi is an accessible and entertaining treasury of information that 'connoisseurs' (French) of the English language will love!