Regardless of how much it weighs, armour is dangerous ! Last year, I read a newspaper report about a man ,in full armour, at a re-enactment or something in, I think, Sweden, who was struck by lightning-----Shocked witnesses reported a hissing sound, and steam coming from the eye-slits in the helmet !! Uuugh !!
    As to the origins of " OK " ----My own pet theory is this :
   Many early Immigrants to America , came from Scotland. Now, when a Scotsman wishes to indicate assent or approval to / of something, he invariably says " Och ! Aye ! " , and it is easy to see how this could have mutated into " OK ", don"t you think ??? At least, it"s more feasible than some of the rather far-fetched and convoluted explanations that I have encountered thus far !!