There are three possible sources of this intriguing name, the first being that it is locational from places in Derbyshire and Herefordshire. Two of the places, near Wirksworth and Hathersage, in Derbyshire derive from the old English pre 7th Century "cald", cold and "hlaw", a hill, while Callow near Mappleton and in Herefordshire get their names from "calu", bare or bald, plus "hlaw", a hill. Another possibility is that this is a Manx name, an Anglicized form of the Gaelic "Mac Caolaidhe", and a patronymic (the "mac" denoting "son of ") from the personal name "Caoladhe", a derivation of "caol", meaning slender or comely. Callow was first introduced in England, via Sussex, from Bordeaux in the 13th Century and a family became established in Norfolk, tracing their ancestry to Nicholas de Kalewe (1286), who it is thought came from a line of Dutch or Flemish traders. Records in London show that the name was reintroduced in the 18th Century by French Huguenot exiles who had fled persecution and sought refuge in Britain, e.g., Anne Caillou, christened at the French Huguenot Church at Threadneedle Street on March 31st 1730. Maria Calow, daughter of Jacobi and Dorotheae Calow, was christened on January 2nd 1676 at St. Martin in the Fields, Westminster. The first recorded spelling of the family name is shown to be that of Brichric se Calewa, which was dated 1070, in the "Old English Bynames of Somerset", during the reign of King William 1, known as "The Conqueror", 1066 - 1087. 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.