Etymologiae (Latin for 'Etymologies'), also known as the Origines ('Origins'), usually abbreviated Orig., is an etymological encyclopedia compiled by the influential Christian bishop Isidore of Seville (c. 560–636) towards the end of his life. Isidore was encouraged to write the book by his friend Braulio, Bishop of Saragossa. Etymologiae summarized and organized a wealth of knowledge from hundreds of classical sources; three of its books are derived largely from Pliny the Elder's Natural History. Isidore acknowledges Pliny, but not his other principal sources, namely Cassiodorus, Servius, and Gaius Julius Solinus.
Etymologiae covers an encyclopedic range of topics. Etymology, the origins of words, is prominent, but the work also covers, among other things, grammar, rhetoric, mathematics, geometry, music, astronomy, medicine, law, the church and heretical sects, pagan philosophers, languages, cities, humans, animals, the physical world, geography, public buildings, roads, metals, rocks, agriculture, war, ships, clothes, food, and tools.