The name Llefelys seems to have been derived from Cligueillus (also spelled Digueillus and Eligueillus in various manuscripts), a character found in Geoffrey of Monmouth's famous pseudo-history "Historia Regum Britanniae", which was early on translated into Welsh as the "Brut y Brenhinedd". Geoffrey makes Cligueillus/Digueillus/Eligueillus the father of Heli and grandfather of Lud, (the prototype of Lludd), Cassibellaunus, and Nennius. In the Welsh "Brut y Brenhinedd", Geoffrey's Heli son of Cligueillus becomes Beli son Manogan, a figure already known to Welsh audiences due to the influence of the 9th-century "Historia Brittonum". Beli is the father of Lludd, Caswallawn, and Nennwy, and Llefelys is added as a fourth son. As such Cligueillus/Llefelys may have been displaced from his position as Beli's father once the well-known figure of Beli was chosen to replace the otherwise unknown Heli.