Yahoo’s Associated Content confirms what I had previously heard about the expression; it began when Roman soldiers were paid with salt. The word “soldier” literally meant “one who is paid in salt.” The pay was either made directly in salt or in “salarium,” which was an allowance for purchasing salt and is the origin of the word “salary.” A person is said to be earning their salary if they are described as being worth their salt. Biblical references for salt usually had positive meanings, such as when Jesus called the disciples “the salt of the earth.”