In his Etymologiae, St Isidore of Seville put together a systematic survey of the world in the form of a vast thesaurus of Latin vocabulary, which supplies a more or less accepted or fanciful etymology for each term. It became one of the most influential books of European culture through the whole medieval period. This Latin 'Roget' is traditionally used as a reference work, accessed through an elaborate index system. In this book Professor Henderson,...