The earliest surviving reference to it is in the Historia Brittonum, which describes a marvelous spring in the regione of Cinlipiuc that has an abundance of fish despite not being fed by a stream.
[2] The Domesday Book refers to a place called Calcebuef, which rendered ten shillings; one editor suggests this is a corruption of Cynllibiwg and that it derives ultimately from the name of Saint Cynllo.
[4] The Red Book of the Exchequer, a mainly 13th-century compilation, mentions a region of seven cantrefs between the Severn and the Wye that had been known as Kenthlebiac during the time of Rhys ab Owain of Deheubarth (died 1078).
[5] This would place Cynllibiwg in the region later known as Rhwng Gwy a Hafren, but reveals nothing about its extent and nature.
The editor suggests that seven cantrefs should be amended to three, perhaps Arwystli, Maelienydd, and Elfael; these are mentioned earlier in the list as part of Powys in the time of 'Meic Menbis', but no longer such.