Oddly, its adhesive properties weren't originally noticed. The inventor didn't check it until after it had dried. Since it wasn't clear enough to make gun sights and there was a war on so he was focusing on that, he put it aside. It was a few years later, after the war, that he went back to it to study it some more and found out about its adhesive properties by unintentionally sticking together some rather expensive optical equipment (he was still interested in it as a potential transparent plastic).
It's surprising how many things have been discovered by people looking for something else. The one that amuses me the most is that the worst-smelling substance known to humanity (thioacetone) was disovered by people looking for a more efficient way to make soap smell nice.
The standard stuff is quite exothermic too, apparently enough to cause damage that way as well as chemically. I've used it on minor cuts and it was fine for that, but it's not really the right tool for the job.