Allegedly, it is one of the ten English words hardest to translate. Serendipity means a “fortunate happenstance” or “pleasant surprise”, the fact of finding interesting or valuable things by chance. Horace Walpole coined the term in 1754, making reference to a Persian fairy tale, The Three Princes of Serendip. The princes, he wrote, were “always making discoveries, by accidents and sagacity, of things which they were not in quest of”. Serendip is the Perso-Arabic name for Sri Lanka (Ceylon).
Here you can read about a possible Hungarian translation of “serendipity”.