Celtic :


Because the Boston Celtics basketball team pronounces its name as if it began with an S, Americans are prone to use this pronunciation of the word as it applies to the Bretons, Cornish, Welsh, Irish and Scots; but the dominant pronunciation among sophisticated US speakers is “keltik.” Just remember: “Celts in kilts.”


Interestingly, the Scots themselves often use the “S” pronunciation, notably in referring to the Glasgow soccer team, the “Celtic Football Club.”