This interesting and unusual surname is of English locational origin from seven places of the name in Westmorland. The placename itself, is composed of the Latin word for castle "Castellum", plus the Anglo-Saxon element "-hlaw", a mound, hence "a castle built on a mound". Thomas, son of Richard Castellhow was christened at Morland, Westmorland, on August 25th 1551. The surname is also recorded in Scotland: William Castelaw was a witness at Failfurd in 1504 according to Scottish records. The surname appears in Stirling in 1532 and Edinburgh in 1567. The church records of the county of Westmorland also record the following entries: Gawan Castlehowe who was christened at Kendel, on January 25th 1619, as was Jas, son of William and Isabel Castelow on May 15th 1774. In London at the church of St. Mary, Magdelane, Bermondsey Anne Castellowe married William Reynolds on November 6th 1563, as did Margarett Castellowe and Thomas Harte on July 5th 1568. The first recorded spelling of the family name is shown to be that of Richard Castalhow, which was dated November 12th 1546, christening witness at Morland, Westmorland, during the reign of King Henry V111, "Good King Hal", 1509 - 1547. 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.