There is plenty of historical evidence that the word 'Fuck' predates its first appearance in the literature. For one, unless the likes of Lyndesay et al. made the word up, it must have been par of the language before it was used in print. For another, there are variants of the word in use going as far back as the middle of the Middle Ages. In addition, the similarity of words in Scandanavian and Germanic languages suggests a history stretching far enough back that it migrated with the migration and integration of those languages into English.
Of course, the Irish also have 'Feck' as far more socially acceptable alternative, but that would be an odd choice of phrase when facing death by gnoll.
