In a letter to Jean-Baptiste Rousseau in March 1719, Voltaire concludes by asking that, if Rousseau wishes to send him a return letter, he do so by addressing it to Monsieur de Voltaire. A postscript explains: "", ("I was so unhappy under the name of Arouet that I have taken another, primarily so as to cease to be confused with the poet Roi.") This probably refers to Adenes le Roi, and the 'oi' diphthong was then pronounced like modern 'ouai', so the similarity to 'Arouet' is clear, and thus, it could well have been part of his rationale. Voltaire is known also to have used at least 178 separate pen names during his lifetime.