According to Nicholas, Cardigan is a compressed form of the ancient Welsh name Ceredigion, so called after Ceredig or Caredig, a legendary king. After the Statutes of Rhuddlan [Edward I days], it became the English designation of this area of Wales.
Thomas Jones was the first to appear in the legal records of Cardiganshire 1558. The plaintiff was John ap Rice ap Powell, and the reason for the suit was a messuage (land and its content) called Tyre dan Yrattgahe alias "Trye evan back". [bundle 99/ No. 40] This records again shows the transition between the Welsh naming system "John ap Rice ap Powell" to "Thomas Jones". In the Welsh system of naming this would be "Thomas ap John ap Rice ap Powell".
Well say hello to Thomas Jones of Cardigan...the first to greet the pages of English documents in this county of Wales.
The history of Cardigan can be found in Nicholas, Vol. I, pp.123-189.