Ciaran in English would be Kevin.

It certainly isn't - as has been pointed out Kevin is the Engkish way of writing the name that can be written in all kinds of impressive ways in Irish, Caoimhín being one of the simpler ways.

In a sense Ciaran is already a partially anglicised form of a name more correctly spelt Ciarán in Irish. A more fully anglicised version is Kieran (since there's no K in Irish.) (And in both spellings they are starting to be quite widely used in England by people without any Irish background, the same as happened to Kevin in a previous generation.)

Neither name has an English or wider European equivalent in the sense that a name like Siobhan or Sean has. Those were names common to other countries in Europe, with the Irish names being translations of them; Ciaran and Kevin, it seems, were Irish names to start with.