... someone not doing his job is said to be "not worth his salt"?
At one time soldiers in ancient Rome were paid, in part, with a ration of salt called a salarium,
from the Latin word sal meaning salt. If a soldier's performance was not up to standard, that
soldier was said to be "not worth his salt."
Later, when the salt was replaced with a money allowance to buy the salt, the allowance itself
was called a salarium. Eventually, salarium came to mean the wages themselves, and this led to our
calling one's pay a salary.
