Recorded as Castake, Costick, Cosstick, Costock, and probably others, this is an English surname. It is locational from a place called Costock in the county of Nottinghamshire, and is first recorded in the famous Domesday |Book of 1086 as "Cortingestoches" from which it is easy to see why it was thought worthwhile to shorten it, by about half! The name translates as "The settlement of Cort's tribe", probably a reference to a people who also inhabited places such as Cosford in Shropshire and Coston in Leicestershire about the time of the Romans (upto 410 a.d.). Locational surnames are usually "from" names. That is to say surnames given to people after they left their original homes to move somewhere else, usually in search of work. Spelling over the centuries being at best erratic, and local accents very thick, often resulted in "sounds like" variations from the base form. In this case the surname drifted down to London in the 17th century and examples of recordings from the surviving church registers of the time include Isaac Costock at the famous church of St Mary-le-Bone, on July 6th 1701, and Fanny Cosstick who married William Brooks at St Pancras Old Church, on December 30th 1863.