This interesting surname is of Anglo-Saxon and Old Norse origin, and is locational from places so called in the East Riding of Yorkshire, and the North Riding of Yorkshire. The placenames are derived from the Olde English pre 7th Century personal name "Alfweard", meaning "elf guardian", and the Olde English "by", meaning a village or homestead, from the Old Norse "byr, baer", similar to the Old Danish and Old Swedish "by"; hence "Alfweard's village or homestead". "By" is frequently found as a second element in the parts of England where Scandinavians settled, such as Yorkshire, Lincolnshire, Leicestershire, Nottinghamshire, Rutland, Cumberland, Westmorland and Lancashire. The place in East Yorkshire was first recorded as "Aluuardebi" and "Alverdebi", in the Domesday Book of 1086, and the place in North Yorkshire was first recorded as "Aluuerdebi" and "Elwordebi", also in the Domesday Book. Recorded in Yorkshire Church Registers are the christenings of Jane, daughter of Richard Ellerby, on November 24th 1579 at Gilling near Helmsley, and of Thomas, son of Wylliam Ellerby, on November 13th 1631 at Oswaldkirk, and the marriage of Miles Ellerby and Ellen Haigh on January 26th 1634 at Leeds. The first recorded spelling of the family name is shown to be that of Willia Ellerbie, which was dated February 7th 1552, christened at Oswaldkirk, Yorkshire, during the reign of King Edward V1, known as "The Boy King", 1547 - 1553. 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.