She was a princess of Ulster, the only daughter of Echu (or Eochaidh), a king in Ireland.
[1] She converted to Christianity, but her father wanted her to marry Corburac, so Saint Patrick intervened on her behalf.
[2][3] Her father agreed to allow her to become a nun, on the condition that Patrick "promised him eternal life without compelling him to be baptized".
[2][4] Cinnia was responsible for the conversion of many pagans and was well known for her miracles, which occurred both during her life and after she died.
[3][4] Hagiographer Agnes Dunbar states that Cinnia might have been Patrick's sister, although that is unlikely.