In 1948, the Irish-language writer Máirtín Ó Cadhain received the kind of rejection letter a novelist might dream of getting. He had submitted his foul-mouthed first novel, “Cré na Cille” (“Churchyard Clay”), to his publisher, only to see it denied on the ground that it was too “Joycean.” This wasn’t meant as a compliment: it was the prudish publisher’s way of calling the book bawdy....