On what date did Fleming coin the name penicillin?

Alexander Fleming coined the name penicillin on 7 March 1929.

Fleming was studying a mould that inhibited the growth of certain bacteria in culture. He called the active substance “penicillin,” deriving the name from Penicillium, the mould genus from which it came. He explained that the term followed the same naming pattern as “digitalin,” a substance associated with the plant genus Digitalis.

The date is distinct from several other milestones. Fleming noticed the contaminated culture after returning to his laboratory on 3 September 1928, although he later referred to 28 September as the date of the discovery. He presented his findings to the Medical Research Club on 13 February 1929 and published his paper in 1929.

Fleming’s early penicillin was unstable and difficult to purify, so his work did not immediately produce a practical medicine. A decade later, researchers at Oxford—including Howard Florey, Ernst Chain and Norman Heatley—developed methods that made penicillin suitable for large-scale therapeutic use.