This interesting and unusual surname is of early medieval English origin, and is a variant of the Scottish name "Cosser", which is an assimilated form of Corsar. The derivation of the name is from the Middle English "corser, corsere" or "courser", a horse dealer, and would have been an occupational name for someone who dealt with horses. Job-descriptive surnames originally denoted the actual occupation of the namebearer, and later became hereditary. Henry Coceur, son and heir of Henry Coceur of Trebroun, granted a charter of lands in Over Lamberton in 1332. Adam Cossour was macer (an official who acts as usher in a court of law) to David 11, and had from his charter a bovate of land with pertinents in the tenement of Aymouthe in the barony of Coldingham (1361). In the modern idiom the surname has many variant spellings ranging from Cossar, Cosser and Cousar, to Couzer, Cowsar, Kowzer and Cowser. Recordings of the surname from English Church Registers include: the marriage of Alexander Couzer and Hester Andrewes on June 24th 1613, at St. James' Clerkenwell, London; the christening of Henry, son of Henry Cowser, on January 8th 1631, at St. Peter and St. Paul's, Marlborough, Wiltshire; and the marriage of Francis Cowser and Mary Rimper in Sunderland, Durham, on February 3rd 1744. The first recorded spelling of the family name is shown to be that of Henry Cosur, granted charter of land, which was dated circa 1320, in the "Register of the Great Seal of Scotland", during the reign of King Robert 1 (Bruce) of Scotland, 1306 - 1329. 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.