The word "agar" comes from agar-agar, the Malay name for red algae from which the jelly is produced. It is also known as Japanese isinglass, Ceylon moss, Jaffna moss or Kanten (Japanese: 寒天 (from the phrase kan-zarashi tokoroten (寒曬心太) or “cold-exposed agar”)).
Agar may have been discovered in Japan in 1658 by Mino Tarōzaemon, an innkeeper in current Fushimi-ku, Kyoto who, according to legend, was said to have discarded surplus seaweed soup and noticed that it gelled later after a winter night's freezing. Over the following centuries, agar became a common gelling agent in several Southeast Asian cuisines.
Agar was first subjected to chemical analysis in 1859 by the French chemist Anselme Payen, who had obtained agar from the marine algae Gelidium corneum.
Beginning in the late 19th century, agar began to be used heavily as a solid medium for growing various microbes. Agar was first described for use in microbiology in 1882 by the German microbiologist Walther Hesse, an assistant working in Robert Koch's laboratory, on the suggestion of his wife Fannie Hesse.Agar quickly supplanted gelatin as the base of microbiological media, due to its higher melting temperature, allowing microbes to be grown at higher temperatures without the media liquefying.