Morkus from Orkus
I'm pretty certain that I saw them appear in a Dragon Magazine during 1e. Just looked it up, they appeared in Dragon #39 in an article entitled Good Hits and Bad Misses.Critical hits first appeared in 2E as an optional rule. The first option was as in 5E (double all dice, add all bonuses once), and the second was rolling additional attack rolls on each successive 20.
Personally, I've gone back and forth on the whole crtical hit thing, as in my thread about using exploding dice instead. I like the idea of a hit becoming "more", but like @Sacrosanct's thread, I like the idea of more than just doing more hp damage.