Serendipity means a "fortunate happenstance" or "pleasant surprise". It was coined by Horace Walpole in 1754. In a letter he wrote to a friend, Walpole explained an unexpected discovery he had made by reference to a Persian fairy tale, The Three Princes of Serendip. The princes, he told his correspondent, were “always making discoveries, by accidents and sagacity, of things which they were not in quest of”.