Fish sauce — that funky, flavor-enhancing fermented condiment — is part of what gives Southeast Asian cooking its distinctive taste. But it turns out, this cornerstone of Eastern cooking actually has a long history on another continent: Europe. And it goes all the way back to the Roman Empire.

Like Asian fish sauces, the Roman version was made by layering fish and salt until it ferments. There are versions made with whole fish, and some with just the blood and guts. Some food historians argue that "garum" referred to one version, and "liquamen" another, while others maintain different terms were popular in different times and places. The current convention is to use garum as a common term for all ancient fish sauces....