The entry for Ciara on this site, mentions St Ciara, dating to the 7th century. Ciar, a character in the Ulster cycle gave his name to Co. Kerry. The Ulster cycle was probably first written down around 700 AD. Some scholars date it to 1 AD, others earlier. In other words Ciar and Ciara as names have existed in Ireland for over a millennium, at least. Old Irish was the language spoken then.
I speak Irish so Keer-a is the 'proper' and instinctive way for me to pronounce Ciara. There is no ambiguity;I don't know what you mean by that exactly.
That doesn't mean I don't recognise that there is a modern US/English name with the spelling, C-I-A-R-A, pronounced "Sierra" or "Key-ara" or whatever. This is a different, separate name to the Irish Ciara, possibly, partly influenced by the popularity of the name Ciara in Ireland from the 1970s on, and inspired by a lack of awareness of Irish language pronunciation.
This message was edited 7/26/2021, 3:02 PM