But "soldaten" or "soldier" is derived from medieval Latin. You really think that the Romans soldiers were paid ("soldij") in salt after they had fought for their empire and risking their lives for years on end?
According to De Vries it is derived from Latin "solidus", or a golden coin.
In the Roman Empire, salt was a product that was hard to win. This made it a valuable and solid product value, and therefore suitable for use as commodity money. The soldiers of the Roman army were paid with salt bars, called Salarium. The current word salary is derived there from.