Moelyci farm, along with most of the adjacent land north and west of Tregarth,  formed part of the medieval township of Cororion, or as it was originally, Creu  yr Wyrion [literally translated as 'the huts of the grandchildren'] mentioned in  the 12th century Mabinogi tale of Math mab Mathonwy. In this story, the wizard Gwydion returns from South Wales with a herd of pigs stolen from the ruler  Pryderi. These are hidden in the 'creu yr wyrion', with 'creu' being taken to  have its particular signification of 'pigsties'. Professor Sir Ifor Williams, born in  Tregarth in 1880, first identified Creu yr Wyrion as Cororion.The Extent of  North Wales made for Edward III in 1352 by John de Delves, refers to the  place as Creweryon. It states that 'in this township there are eight free  gafaelion [holdings or tenements] namely Gafael Gronw ap Eden, Gafael  Iorwerth ap Llion, Gafael Howell ap Kefuth, Gafael Arthergon, Gafael Goyll,  Gafael Edeneweyn, Gafael Kennyn and Gafael Griffri'. These gafaelion were  at this time [1352] said to be in the possession of the grandsons of those  named. A remarkable map drawn up by Lord Penrhyn's agent Wyatt, around  1800, shows the location of these ancient holdings in relation to the Penrhyn  Estate. Moelyci corresponds in part or wholly with Gafael Goyll. The vill of  Cororion once extended as far south as Capel Curig, corresponding with the  description of Creu yr Wyrion township in the Mabinogi as being 'the highest  in North Wales'. References to Moelyci, spelled in various ways, occur in the  Penrhyn Manuscripts from 1588 onwards.