Cate Kerr, Beyond the Fields We Know
We use the word serendipity to describe situations in which we discover something wonderful by accident - often when we are searching for something else entirely. In other words, we stumble upon wonders when we are least expecting them, tripping right over things before realizing that we have found something astonishing.
The root form is Serendip, an old name for Sri Lanka (formerly Ceylon) hailing from the Arabic Sarandib, then the Tamil Seren deevu or Sanskrit Suvarnadweepa meaning "golden island", possibly related to Simhaladvipa meaning, "Dwelling-Place-of-Lions Island". If so, the origins of serendipity go back a very long way indeed, for the only lions on the island were extinct long before modern man arrived, and little evidence of them ever been found.
The adjective form has been around since 1754 when Horace Walpole used it in a letter to a friend, explaining that he had derived it from an old Persian fairytale called "The Three Princes of Serendip". The three royal gentlemen in that tale were on a quest and always finding things they were not looking for and had no need of. Walpole was making an important point in his letter - that a fey and subtle wisdom is often at work in serendipitous situations, a canny ability to see relationships between ostensibly irrelevant facts and come to important conclusions from them.