This interesting surname has two distinct possible sources, each with its own history and derivation. Firstly, Riddle may be of Anglo-Saxon origin, and a locational name from any of the various Northern English or Scottish places named with the Olde English pre 7th Century "ryge", rye, and "dael", valley, cognate with the Old Scandinavian "dal(r)", valley. These places include: Rydal (Westmorland); Ryedale (the North Riding of Yorkshire); Riddell, south west of Lilliesleaf in Roxburghshire, and the ancient seat of Ryedale in Kirkcudbrightshire. Locational surnames were originally given to local landowners, and the lord of the manor, and especially to those former inhabitants who left their place of origin to settle elsewhere, and were best identified by their former village name. The second possibility is that Riddle derives from the Old French personal byname "Ridel", literally meaning "small hill", and used here in a transferred sense to describe a rotund or stockily-built man. One Ridel Papillun was noted in the 1163 Pipe Rolls of Lincolnshire. Early examples of the surname include: Gaisfridus Ridel, entered in the Domesday Book of 1086 for Cheshire; Walter de Riddel (of Ryedale, Yorkshire), who accompanied King David 1 (1124 - 1153) from England and was appointed sheriff of Yorkshire, and Sir William de Riddell, who became constable of Norham castle, Northumberland, in 1314. Edward Riddle (1788 - 1854), mathematician and astronomer, was mathematical master of the Royal Naval Hospital, Greenwich, 1821 - 1851. The first recorded spelling of the family name is shown to be that of Galfridus Ridel, which was dated 1048, in the "Early Medieval Records of Scotland", during the reign of MacBeth, known as "The Usurper", 1040 - 1057. Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.