When we say someone is worth their salt, we mean literally that he or she earns whatever reward they get, which usually refers to their paycheck, but can also simply denote a person who is worthy of respect or admiration.
But how did salt come to be a measurement of worth?
It is very simple. The expression “worth his salt” or “earning his salt,” at origin, literally meant “worth his pay.”
The expression has sometimes, as well, been expanded to “worth his weight in salt.” All of this reflects the fact that salt is a mineral that has been a commodity in every part of the world, throughout history.
People bartered with it and may have actually carried cakes of salt around with them.
If you could carry your weight in salt then you had a lot of spending power!
At times, according to some sources, Roman soldiers were paid partly or fully in salt.
Or, they were given an allowance for buying salt.
In fact, the Latin word for salt was sal and these salt rations, or salt allowances were called a salarium, from which we derive our modern word salary.
Not only that, but the word soldier actually comes via the French word solde, meaning pay, and a soldier was “one who is paid.” However, these terms derive from the Latin word solidus, which was the name of a solid gold coin. You can see, though, that the word soldier did not mean someone who is trained to fight, but someone who is paid to fight.
Most explanations of the expression’s roots give the Roman practice as the precise origin, but the use of salt as barter material or even money is not unique to the Romans. Some sources cite the use of salt as a barter for slaves, so that “worth his salt” would have a quite literal meaning.
There is also a story the the modern expression comes from the practice of pirates being paid in “salted beef,” so that a pirate who wasn’t doing his job wasn’t “worth his salt.”
If you spend any time researching the origin of familiar expressions, however, you will find that there is always a pirate story in the mix!