What is the source of the antibiotic pencillin?

Joseph Lister, an English surgeon and the father of modern antisepsis, was prompted by Burdon-Sanderson's discovery to investigate and describe in 1871 that urine samples contaminated with mould did not allow the growth of bacteria. He also described the antibacterial action on human tissue on what he called Penicillium glaucum. A nurse at King's College Hospital whose wounds did not respond to any antiseptic, was then given another substance that cured her, and Lister's registrar informed her that it was called Penicillium.

Greeks often used mouldy bread to treat wounds, so penicillin/illium has been used since ancient times, even though it had no name, and wasn't entirely understood.