The word salary derives from the Middle English
from the Latin salarium
which is related to the Latin
meaning salt. This comes to English by way of France (the Norman Conquest
brought many words related to economics
, and law
into English) salaire
. The phrase 'worth its salt' is related to this phrase which is quite similar to 'worth its weight in gold'.
In ancient times, a person was literally worth their salt. This dates back to Roman times with building roads and fighting wars. Such a workout would reduce the body reserves of salt (today we see sports drinks such as Gatorade that replenish the sodium and potassium (electrolytes) that are lost through sweat). To survive, these soldiers needed to buy salt - the wages were paid for the purpose of buying salt. In some cases the salarium was paid in salt itself.
The salarium was paid on a regular basis. As the need for salt was reduced (technology made getting salt easier) the name became less associated with the purchase of salt and instead was a monetary payment that person received periodically for work done.
Salt was used as a currency in Ethiopia as recently as 1935. Within Ethiopia, the phrase "he eats salt" is said of a person who spends too much money. Salt was preferable as a currency to gold and silver. Two bars of salt were worth
about 16 kilograms of wheat.