It was known to both Pliny and Plutarch, in the first century A.D., that oil poured upon a stormy sea would quiet the waves.
Five centuries later, according to the Venerable Bede, Bishop Aidan, an Irish monk of Iona, also knew this “miracle,” for after foretelling that a storm would arise, he gave e seamen of a certain vessel some holy oil and advised them to pour it upon the water to calm, the sea and permit the vessel to ride through the storm.
But, perhaps because oil was not plentiful, this knowledge seems either to have been lost or to have remained a scientific fact, for we do not find it again referred to until Benjamin Franklin, in 1774, refers to Pliny’s statement in some correspondence.
But when whale fishing became a great industry, beginning toward the end of the eighteenth century, and oil in large quantities was available, especially on whaling vessels, it is likely that the scientific phenomenon was often made use of.
By the middle of the nineteenth century, at least, the fact was so well known that the expression began to be used metaphorically. Oil poured on troubled waters, as we use it today, means something offered for easing a troubled condition.