Old English wǣrloga traitor, scoundrel, the Devil, from wǣr faith, troth + -loga from lēogan to lie. The sense ‘the Devil’ probably comes from the idea of the Devil as a traitor to God; this led in Middle English to the sense ‘one in league with the Devil’, having or using occult powers. From the 15th cent. the word was mainly Scots, until popularized by Sir Walter Scott in the 19th cent