Serendipity: An accidental and fortunate discovery.
A celebrated instance of serendipity in biomedical research took place in 1928 at St Mary's Hospital in London. While studying staphylococci (staph bacteria), the physician and microbiologist Alexander Fleming happened to noticed that on a dish containing agar on which he had been growing germs, near some mold, the germs were less common. He grew more of the mold and named it penicillin from its Latin name Penicillium. Fleming found the mould was effective against bacteria that caused diseases such as anthrax, meningitis and diphtheria.
The word serendipity was coined by Horace Walpole in the fairy tale The Three Princes of Serendip (1754). Serendip was an old Persian name for Sri Lanka.