This is a genuine Norman Invasion name introduced at the 1066 Conquest of which at least eleven alternative spellings exist. It is a French locational name which comes from one of the five villages called Ovillys in Calvados, Normandy, although the first invaders were from Ovilly le Basset or Ovilly le Vicomte. Locational surnames were developed when former inhabitants of a place moved to another area, usually to seek work, and were best identified by the name of their birthplace.The name development includes: Robert Oilgi, also in the Domesday Book, Henri de Olli (1135, Oxford), Henry de Oly (1212, Oxford), Reginald Duly (1297, Yorkshire), John Dolye (1272, Staffordshire), Robert de Doley (Oxfordshire, 1279) and Robert de Oylly (1378, Oxfordshire). The first recorded spelling of the family name is shown to be that of Robert de Oilleio, which was dated 1086, The Domesday Book, Oxfordshire, during the reign of King William 1, known as "The Conqueror", 1066 - 1086. 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.