This interesting and unusual name is of Medieval English origin, and is one of the many short, variant, forms of the ultimately Germanic personal name 'Theudoric', which is composed of the elements 'theudo', people, race, and 'ric', power. The personal name appears in Old English (pre 7th Century) as 'Theodric', and the Normans introduced their adopted short forms of the Germanic name, as 'Terry, Therry' and the Old French 'Thierri', after the Conquest of 1066. In England the personal name is first recorded in the Domesday Book of 1086 as Theodricus and Tedric(us), while the development of the surname includes Thomas Therry (1243, Somerset), John Therrich (1327, Suffolk) and in London, Alice Thayre (1562), Ann Thaier (1592) and Edward Thai (1640). The modern surname can be found as Theyer or Thayer. The christening of Humphrey Theyer was recorded at Christchurch, Newgate, London, on August 3rd 1677. The first recorded spelling of the family name is shown to be that of Ralph Teri, which was dated 1199, Register of the Freemen of Leicester, during the reign of King Richard 1, 'The Lionheart', 1189-1199. 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.