Recorded as Thorlby and the dialectal Thorby, this is an English surname, although in sense one of pre 7th century Danish-Viking origins. It is locational deriving from a place called Thorlby near Skipton in North Yorkshire. The place is recorded in the Domesday Book of 1086 as "Torederebi" and appears as "Thorledby" in the county pipe rolls of the year 1315. The name means "Thor's homestead", from the Old Scandinavian name "Thor", a divine name used for the god of thunder in early mythology, and preserved in the weekday name of Thursday, with "by", a farmstead or village. Locational surnames were acquired especially by those former inhabitants of a place who had moved to another area, and were thereafter best identified by the name of their birthplace. Spelling being at best erratic and local dialects very thich lead to the development of 'sounds like' spellings. Amongst the recordings of the name those of Robert Thorlby, at Witham-on-the-Hill, on January 12th 1668, the marriage of John Thorlby and Alice Brierhurst on May 14th 1761, at Fulbeck, and in London John Thorby at St James Clerkenwell on December 11th 1668. Surnames became necessary when governments introduced personal taxation. In England this was sometimes known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.