Liquamen is an ancient sauce made by the Romans a long, long time ago. Imagine you are making soup, but you want it to taste very, very good. So you take a whole bunch of fish, put them in a pot with salt, spices, and water, and then heat them up until all the flavors mix together. Then you strain out all the fish parts and what you are left with is a very tasty liquid that is called liquamen.
The Romans really liked this sauce and used it to make many different dishes taste better. They would add liquamen to their stews, their roasted meats, and even their sweet desserts. It was like magic! All the food tasted so much better with just a little bit of this sauce. And because it was made from fish, it was also very healthy for them.
Today, we don't use liquamen much anymore, but there are still some people who like to cook with it. It's kind of like a special secret ingredient that makes everything taste better. So if you ever hear someone talking about liquamen, just remember that it's an ancient fish sauce that makes food taste really good.