This very unusual and rare name is apparently habitational from a now unidentified spot near Garstang in West Lancashire, the "modern" spelling has undergone some considerable changes even from it's earliest seventeenth Century recordings as shown below. However research suggests that the origination is Norse-Viking-Irish of the 9th Century, the development being from the Norse "kill" meaning a narrow valley or inlet plus the Irish/Old English "Cruc or Cros" which does mean "cross", but in the sense of this name suggests a valley in the shape of a cross. This particular area was invaded and controlled by Norse-Irish throughout the 9th Century. The present spelling appears to be a reversion to the "original", recordings include William Kilcrash of Garstang in 1718, William Killcress of Manchester in 1850, and Lewis Killcross who married Sara Lowe at Manchester Cathedral on July 7th 1859. The first recorded spelling of the family name is shown to be that of Mary Killcrash, which was dated May 5th 1678, married Roger Berches at Garstang, lancashire, during the reign of King Charles 11, "The Merry Monarch", 1660 - 1685. 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.