WD stands for water displacement and the 40 is to denote that was the 40th attempt at a formula that would work. It was developed for outer space use. It technically is not a lubricant although WD-40 does make other products at do lubricate but rather a rust preventer.
The purpose was to push water out and replace it with a secret formula of liquid to make it non conductive.
2014 Palomino Puma 25RS
2011 F-150 Super Crew XLT
Days camped in 2014 - 23
Camped 2015 - 47
Camped 2016 - 51 done - 6 more planned so far