Silver has been used as currency for millennia. Archaeological evidence has shown that it was being separated from lead as far back as 6,000 years ago. The most well known use of it as currency is described in the Bible. Judas is infamous for taking thirty silver coins to turn Jesus Christ over to the Romans.
Silver has the highest thermal and electrical conductivity of all metals. Its properties allow it to provoke or speed up chemical reactions. For instance, during long sea voyages throughout the ages, sailors would place silver coins in barrels of water and wine to keep the liquid drinkable, and pioneers crossing the Great Plains used the same idea.
This might be more than you wanted to know about silver but its properties are key to its destructive capabilities towards demons.