Garum is a fish sauce that was highly prized as a seasoning in Ancient Rome. It was made of fermented fish. Recently people have tried to recreate it according to surviving evidence, but I've seen reenactors soak anchovies in vinegar for a week and then strain out the chunks.
Very fine erudite commentaries adorn this page. Thank you. I humbly wanted to propose to Duo that " garum " be accepted in the English version as translation for " garum ", and viceversa. Version et thème, comme disent les Français. It is sufficiently specific and known to be recognized.