WD.... stands for Water Displacing
40..... stands for "the first 39 formulations didn't work"
If your having trouble with water on electrical products causing issues it might be useful to sheet off the water.
It's not really a very good cleaner nor is it a lubricant....and in fact will remove what oil you might have on the surface when it evaporates leaving you worse than when you started. (Which is likely why Zip Dee says don't use it)
This stuff was sold to the military when there was lots of arcing and problems when water got into things like distributor caps on vehicles. They could spray the whole thing with this "Stuff" and it would sheet the water off.
The military bought the stuff by the truckload and there was always boxes of the stuff laying around so it got used for everything.
In a brilliant marketing move the makers started to sell it as a sort of snake oil that's good for whatever ails you mechanically.
And now you know the rest of the story
What your looking for is a dry lubricant that won't attract and hold the dirt...