WD-40's birthday this fall. The product was the success of Norm Larsen's 40th attempt to develop an anti-corrosion agent cum moisture repellent for NASA. WD-40: “Water Displacement - 40th Attempt".
The stuff soon turned out to be very versatile and even became the source of all sorts of monkey sandwich stories. The formula is apparently strictly secret and according to technician Werner D. "Diesel with some sulfur oxide". So that is also arranged with this.
Also interesting is Werner's reference to a weapon site: Never use WD-40 to clean / lubricate weapons. WD-40 is water-attracting (translation from English).
A water expeller that attracts water? Check with the birthday boy