Recorded in the spellings of Tiddy and the much rarer Tidy, this is a Cornish locational surname of post medieval origins. The name means "one who was resident by the River Tiddy", from the pre 7th century Olde English and Cornish-Breton "tudie" meaning clear or good. Locational surnames were usually "from" names, which is to say that they were given to people after they left their original homes, for whatever reason, and moved elsewhere. "Elsewhere" could be the next village, which seems to be generally the case in Cornwall, although in other parts of the United Kingdom, it could, and often was, as far away as London. Nethertheless the same principle applied that the easiest way to identify a "stranger" was to call him or her, by the name of the place from whence they came. Local dialects being thick, and spelling being at best erratic, often lead to the development of many and sometimes colourful forms, some barely recognizeable. In this case early examples of the surname recordings taken from surviving church registers includes Allin Tiddy, who married Susan Prust at Bodmin, on July 20th 1619, and Jane Tiddy, who married Richard Harrison at Truro on October 20th 1655. The earliest church recording is believed to be that of Margaret Tiddy, who married Francis Bourne at Bodmin, on April 24th 1608. This was during the reign of Queen Elizabeth 1st of England, 1558 - 1603.