They rest in your fridge or kitchen pantry, minding their own business. But your condiments have lives beyond your dinner plate. Sometimes the secrets are ancient and shrouded in mystery. Sometimes they're the result of business and culinary wrangling. But they all add a new, deeper dimension to that sauce you slop on your plate.

1. WORCESTER OR WORCESTERSHIRE SAUCE

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WHAT YOU THINK IT IS: A difficult-to-pronounce mixture with an old-time label.

ITS SECRET: Behind that label, you'll find a tale of empire, British chemists, and an accidental discovery.

The sauce you know and (possibly) love was first made in England’s Worcester County, but its true origins are in South Asia. Lord Sandys, a British nobleman, had spent time in Bengal in the early 1800s and became enamored with a local sauce.

When he came home, he gave a recipe to a pair of local chemists—John Lea and William Perrins. They whipped up a batch but found the taste decidedly disagreeable. Perhaps wanting to spare themselves from any unpleasantness with the lord, they packed the mixture away in the cellar and forgot all about it.

Years later, they came upon their containers of sauce and—being true tinkerers of the old school—decided to taste it. They found that aging had mellowed the flavor, producing a delicious result. The sauce, named Lea and Perrins after its accidental creators, became an instant hit in Europe after going on sale in 1838 and was imported to the United States the next year.

2. TOMATO KETCHUP

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WHAT YOU THINK IT IS: An all-American tomato reduction that goes great on everything.

ITS SECRET: An ancient sauce achieved its modern form by avoiding preservatives.

Ketchup has been around in various forms since at least the 1600s. Some of these early versions were based on mushrooms and fish. It wasn’t until the early 1800s that tomato variants became popular (many people still believed that tomatoes were poisonous). Even then, the sauce was thin and watery.

But change was in the air in the late 1800s and early 1900s. Commercial food production was spreading, and the tomato ketchups available were awful, and loaded with preservatives. Coal tar was tossed in to make the sauce red.

Food magnate Henry J. Heinz thought he could do better. He set his chief food scientist, G.F. Mason, the task of finding a tomato ketchup recipe that didn’t use preservatives. Mason came up with a recipe in 1904—it used ripe tomatoes, whose pectin helped make a thicker sauce, and more salt, sugar, and vinegar than competitors' concoctions. The natural preservative qualities of those ingredients meant Heinz could avoid, say, benzoic acid, and offer an all-natural product.

He put the finished result in a clear bottle to highlight its freshness, and within two years the Heinz company was cranking out five million bottles of the stuff.

3. MAYONNAISE

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WHAT YOU THINK IT IS: A comforting white concoction that you never want to leave outside the fridge.

ITS SECRET: Despite an unsanitary reputation, mayonnaise has a secret life as a germ-fighter.

Ask anyone who cooks, and they will probably warn you about mayonnaise. It goes bad easily, they claim. Watch out for food poisoning!

As a matter of fact, though, mayonnaise's reputation is almost entirely undeserved. The modern condiment is made using pasteurized eggs, meaning there’s little risk of salmonella. And the spread includes lots of salt, vinegar, and lemon juice. Some studies have suggested that the high acidity and salt level in modern, commercially produced mayo can actually slow the growth of bacteria, or even prevent it entirely.

So why the bad rap? It’s simple. Mayonnaise is an emulsion, which means that it’s made from two base ingredients that don’t mix naturally (in this case, oil and either vinegar or lemon juice). To make the ingredients cohere, you need an emulsifier—and egg yolk is the most common. Homemade versions often call for raw eggs, which can be risky.

There’s another problem, too. Mayo is often used with chicken, potatoes, ham, and other low-acid foods that can be at risk of bacterial contamination. But don’t blame the spread!

4. SOY SAUCE

WHAT YOU THINK IT IS: A salty concoction used in Asian cuisine.

ITS SECRET: It’s produced by an ancient family business spreading its influence around the globe.

Soy sauce can be traced back to the ancient Chinese jiang, a combination of preserved foods with spices. Jiang was created in several ways—some used meat and seasonings, some used fish and seasonings, and some used grain and seasonings.

That last variety of jiang (often made from soybeans and wheat) was the ancestor of modern soy sauce. The sauce made its way to Japan, evolved a bit, and by the 1600s was a fixture in the island nation. At the same time, the Mogi and Takanashi families started brewing the stuff. The small businesses grew, and in 1917, the Mogi and Takanashi operations, along with others, were merged into the Noda Shoyu Co.

In 1964, that company changed its name to Kikkoman. That means that the most common name in soy sauce has been manufactured by a line that goes back further than three centuries. (And the company hasn’t stopped growing, either; the company now ships its soy sauce to more than 100 countries around the world.)