How did the expression "he was born with a silver spoon in his mouth" came about?

Actually, the expression came from an old custom of godparents who give gift of a spoon to a child at his christening. The gift signifies their responsibility for its nourishments and well-being. If the celebrating child is wealthy, the spoon was usually silver, otherwise, it would be pewter or tin.

Since then, if someone was given a silver spoon as a gift he is said to be "born with a silver spoon in his mouth". It means that he was born into wealth rather than having had to earn it.