The English language that is spoken by one billion people around the world is a linguistic mongrel, its vocabulary a diverse mix resulting from centuries of borrowing from other tongues. From the Celtic languages of pre-Roman Britain to Norman French; from the Vikings' Old Scandinavian to Persian, Sanskrit, Algonquian, Cantonese and Hawaiian – amongst a host of others – we have enriched our modern language with such words as tulip, slogan, doolally, avocado, moccasin, ketchup and ukulele.