Hi Tom
Your right about local Killie folk calling us Carrwal with the pronunciation on the first syllable similar to Caer in Caerlisle which I know means castle and is a Welsh/ancient British word. Second Syllable "wal" with "a' sounding "ah'.
Even when I lived in Wigtownshire there were people who would call me "Caerwal". Strangely I always thought that Carswell seemed more akin to Caerwal but they were never called that to my recollection David