Garum

Garum was a fermented fish sauce used as a condiment in the cuisines of ancient Greece, Rome, and Byzantium. Liquamen was a similar preparation, and at times the two were synonymous. Although it enjoyed its greatest popularity in the Roman world, the sauce was earlier used by the Greeks.

What is called liquamen is thus made: the intestines of fish are thrown into a vessel, and are salted; and small fish, especially atherinae, or small mullets, or maenae, or lycostomi, or any small fish, are all salted in the same manner; and they are seasoned in the sun, and frequently turned; and when they have been seasoned in the heat, the garum is thus taken from them. A small basket of close texture is laid in the vessel filled with the small fish already mentioned, and the garum will flow into the basket; and they take up what has been percolated through the basket, which is called liquamen; and the remainder of the feculence is made into allec.

  –from the 10th century Byzantine manual Geōponika: Agricultural pursuits, Vol. II, pp. 299-300; translated from the Greek by Thomas Owen; London 1806.

Pliny the Elder and Isidore of Seville derive the Latin word garum from the Greek γαρός (garos), a food named by Aristophanes, Sophocles, and Aeschylus. Garos may have been a type of fish, or a fish sauce similar to garum. Pliny stated that garum was made from fish intestines, with salt, creating a liquor, the garum, and a sediment named (h)allec or allex. A concentrated garum evaporated down to a thick paste with salt crystals was called muria; it would have been rich in protein, amino acids, minerals and B vitamins.

Like the modern fermented soy product soy sauce, fermented garum is rich in the natural amino acid monosodium glutamate, a source of umami flavoring. It was used along with murri in medieval Byzantine and Arab cuisine to give a savory flavor to dishes. Murri may well derive from garum.

...
Wikipedia