This interesting surname with variant spellings Carlow, Carlo, Carlaw, etc., is a dialectal variant of the locational names Callow in Derbyshire and Hertfordshire, deriving from the old English pre 7th Century "calu" meaning "bere" plus "hlaw" "hill", hence "bare hill", or Calow in Derbyshire, deriving from the old English pre 7th Century "calu" plus "halh" meaning "corner of land", "water meadow". It may also be a topographical name deriving from the old English pre 7th century "carr" meaning "rock", "stone" plus "hlaew", "burial mound" (sometimes used as meeting-places). The surname dates back to the early 17th Century, (see below). Further recordings include one Thomas Carlo who married Mary Harwood at St. Katherine by the Tower, London, on February 8th 1689, and Charles, son of Thomas and Anne Carlow, who was christened on August 20th 1708, at St. James, Clerkenwell, London. One David Carlow, aged 20 yrs., a famine emigrant, sailed from Liverpool aboard the "Howard" bound for New York on May 18th 1847. The first recorded spelling of the family name is shown to be that of Susan Carlew married William Webb, which was dated 1638, St. Mary Magdalene, Old Fish Street, London, during the reign of King Charles 1, "The Martyr", 1625 - 1649. 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.