The name WD-40 stands for “Water Displacement, 40th formula.” The Rocket Chemical Company in San Diego reportedly reached the successful formula in 1953 after 39 earlier attempts.
Its first major industrial use was by aerospace contractor Convair, which used WD-40 to protect the outer skin of the Atlas missile from corrosion. This connected the product directly to Cold War-era missile development.
Over time, WD-40 moved from aerospace hardware into everyday homes and workshops, where people began using it on hinges, tools, bolts, and other metal parts. Its unusual history explains how a product created for advanced technology became a familiar household item.
