This interesting name is of Old Norse origin, and is a locational surname deriving from any one of the places called Dalby, in Lincolnshire, near Spilsby; in Leicestershire near Melton Mowbray, and in North Yorkshire near Terrington. All three places are recorded in the Domesday Book of 1086 as "Dalbi", and all share the same meaning and derivation, which is "the farm in the valley", from the Old Norse "dalr", valley, with "byr", farm, settlement. The surname is found most frequently in Yorkshire, and therefore probably derives mainly from Dalby in that county. Locational surname s were mostly acquired by those former inhabitants of a place who had moved to another area, and were thereafter best identified by the name of their birthplace. The modern surname can be found as Dalby, Dalbey, Daulby, and the apparently Norman form D' Aulby. Among the recordings of the name is Yorkshire is that of the christening of Thomas Dalby, son of Richard, at Brandesburton, on May 6th 1585. The first recorded spelling of the family name is shown to be that of Matthew de Dalbi, which was dated circa 1160, in Documents relating to the Danelaw (Lincolnshire), during the reign of King Henry 11, known as "The Builder of Churches", 1154 - 1189. 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.