In The Beginning:

“Some years ago, after writing a book, The Celtic World, I received a letter from an American. He was, he said, an alcoholic and it had worried him but having read of the Celtic love of wine – a story told by the Classical writer Athenaeus of the Gauls – he was much reassured. His grandparents had been Celts from Scotland and his behaviour was thus explained: it was part of his Celticness and he would henceforth be proud of it. Many reading this might find it an innocuous story, and might indeed gain some reassurance for their own occasional overindulgences, but others might become apoplectic seeing in it yet further evidence of the insidious Celtic myth perpetuated by popular books. One academic member of this camp has even gone so far as to suggest that some authors deliberately use the word ‘Celtic’ in book titles to boost sales."

From: The Celts – A Very Short Introduction by Barry Cunliffe