This very unusual surname is in effect a variant of Cavis, itself an anglicised development of the ancient gaelic "MacThamais", originally recorded only in County Cavan, Ireland. "Thamais" is the ancient Irish form of the hebrew Thomas, meaning "The Twin" and this name was probably introduced by St Patrick in the 6th century a.d. but maybe later, and possibly a Crusader introduction. The surname spelling was changed to MacCavish in the 16th century, the shortened form as Cavish being first recorded in England in the early 17th century. There is a body of opinion that suggests that the name may also be a dialectal patronymic of the Yorkshire surname "Cave" (from the village so named), and this is possible, as both Caves and Keaves are recorded in Ireland. Names of disputed origins often develop several variant forms, and this is so in this case. Certainly the early form is Cavis, in addition to the first recording below, we have Thomas Cavis, who married Elizabeth Gercey at the church of St Katherines by the Tower, London, on May 11th 1606, whilst on May 26th 1686, we have a changed form when Philip Cavss or Causs (the spelling is unclear) and his wife Elizabeth, were witnesses at the christening of their son Joseph, at the same church of St Katherines. Nearly two centuries later Francis William Kevis, the son of James and Harriet Kevis, was christened at Holy Trinity, Kingsway, London, on January 1st 1852. The first recorded spelling of the family name is shown to be that of Christian Cavis, which was dated April 25th 1602, married Thomas Bourros, at St Giles Church, Cripplegate, London, during the reign of Queen Elizabeth 1, known as "Good Queen Bess" 1558 - 1603. 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.