Tolkien was a professional linguist and a specialist in the Old English language. Tolkien rendered Rohirric, related to an older form of Westron, by the Mercian dialect of Old English, spoken in the English Midlands. Tolkien taught courses in Old English heroic verse, history of English, various Old English and Middle English texts, Old and Middle English philology, introductory Germanic philology, Gothic, Old Icelandic, and Medieval Welsh. Mercian differed slightly from the West Saxon dialect in which most surving Old English documents are written. Tolkien considered it his favourite Old English dialect and once said that ideally he would speak nothing but Old Mercian.