Take care of yourself; be prepared. This phrase was uttered by Oliver Cromwell in 1642, when his regiment was about to attack the enemy at the battle of Edgehill. “Put your trust in God,” he told his troops, “but keep your powder dry.” Wet gunpowder was very difficult to ignite, and with it a soldier would in effect be unarmed. The term was transferred to other enterprises in the nineteenth century. In the twentieth century it was sometimes used jocularly to mean a woman’s makeup (face powder).