English, from Greek "God giving" or "gift of God".
The French form is accented: Théodore.
Note: Theodore has a similar meaning to Dieudonne, Dorothy, Matthew, Nathaniel and other names. We have classed these as lesser synonyms.
The 1841 Census of Aberdeenshire has a number of very rare spelling variations but all should be found using Soundex searching.
The Welsh name Tudur had been Anglicized as Theodore but, while this is believed to be incorrect, there is the possibility of historic Welsh records using either name.