Irish Ancestors' Surname History, the surname Dyer is an anglicized version of Ó Duibhir (grandson of the dark brown [man]) or Mac Duibhir (son of the dark brown [man]). This variant is found in counties Sligo and Roscommon.
Irish Ancestors also includes information from the surname dictionary Sloinnte na hÉireann. According to this dictionary, the surname Dyer is found in county Mayo, Belfast, and scattered other areas. Dyer is an English occupational name. It is also a form of the Irish name Mac Duibhir, and is also found as MacDyer.
My known Dyer ancestors are:
2nd-great-grandmother: Sarah Claire "Sadie" Dyer
born 8 October 1863, Nashville, Davidson Co., Tennesssee
married John William Morton Gatlin 26 June 1881, Nashville, Davidson Co., Tennessee
died 20 January 1945, Chicago, Cook Co., Illinois
3rd-great-grandfather: Michael Dyer
born about 1829, Co. Roscommon, Ireland
died 3 June 1870, Nashville, Davidson Co., Tennessee