Well, that one opened up a can of worms!  Originally, WD40 was called
"Rocket WD40" over here in the UK.  It came about as one of those
spin-off products from the space industries of the 1960's or so we
were told -- a bit like Velcro was.

It was billed as a water repellent, and many-a-damp ignition system was
bought back to life just by spraying it all over the plugs and leads.
It could also be sprayed under the distributor cap and on the points as
well.  It was an electrical insulator and, although there may be some
finite lubricant present, its primary function was to penetrate and
dispel moisture.

I seem to remember a demonstration many years ago where an electric
drill was soaked in the stuff and held underwater and switched on.
No, the demonstrator was not electrocuted!

That's it for what it's worth,
Kind regards from
Paul Camps - in the boiling hot UK; well, it's only 35 degrees C.