Serendipity is a propensity for making fortuitous discoveries while looking for something unrelated.

It was coined by Horace Walpole on 28 January 1754 in a letter he wrote to his friend Horace Mann, an Englishman then living in Florence. The letter read,

"It was once when I read a silly fairy tale, called The Three Princes of Serendip: as their highnesses traveled, they were always making discoveries, by accidents and sagacity, of things which they were not in quest of: 

"Serendipity is looking in a haystack for a needle and discovering a farmer's daughter." Laurence Block

"You have to set out in good faith for elsewhere and lose your bearings… serendipitously." Isaac Asimov