This extraordinary surname is English and recorded in a wide variety of spellings. These include Castocke, Castlake, Castice, Caustic, Caustick, Costick and Costock, the very number and variation of the spellings indicating that the origin is open to dispute. In our opinion the name is definately locational and originates either from a now "lost" pre 7th century medieval village possibly called "Cas-wic" or similar, and meaning the "the watercress (cas) farm (wic)", or from some existing place such as Calstock in the Isle of White, or Costock near Nottingham. It is difficult to be more precise, particularly when the surname spelling is so widely transposed. What is not in arguement is that the surname has been widely recorded in its different spellings for several centuries. These recordings include Samuel Costick, who on January 18th 1818, married Mary Weller at Kingston on Thames. They seem to have lived all their life in Croydon, and curiously whilst they are recorded there upto 1830 as "Costick, on December 25th, Christmas Day, 1831, when their son William was christened, they are then recorded in the spelling of "Caustic", a spelling which they apparently retain. The first known recording of the surname in any spelling is believed to be that of Christopher Castocke, who married Elizabeth Johnson at St Botolphs church, Bishopgate, London, on March 11th 1611. This was in the reign of King James 1st, 1603 - 1625.