Read this: The term "Enlightenment" emerged in English in the later part of the 19th century, with particular reference to French philosophy, as the equivalent of the French term 'Lumières' (used first by Dubos in 1733 and already well established by 1751). From Immanuel Kant's 1784 essay "Beantwortung der Frage: Was ist Aufklärung?" ("Answering the Question: What is Enlightenment?") the German term became 'Aufklärung' (aufklären = to illuminate; sich aufklären = to clear up). However, scholars have never agreed on a definition of the Enlightenment, or on its chronological or geographical extent. Terms like "les Lumières" (French), "illuminismo" (Italian), "ilustración" (Spanish) and "Aufklärung" (German) referred to partly overlapping movements. Not until the late nineteenth century did English scholars agree they were talking about "the Enlightenment."
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): In what century did the term Enlightenment emerge in English?
19th