This tune was definitely in tune collections around 1750-60 in both England and Scotland, and it is such a basic tune that it's not surprising to find similar tunes in other traditions. In any case, plenty of amateur and professional musicians and dancing masters were travelling around Europe in the 1700s, so any good tune was bound to travel widely. It was in America before 1800, again not suprising based on the number of immigrants and the many officers and soldiers who crossed the pond. Sometimes you hear people claim that its name relates to morphine or drug use, but since the tune was around in the 1700s and morphine didnt get widely used until the 1850s, it's much more likely that morphine took its nickname from the tune rather than the other way around. I have never met a fiddler above the beginner level who didnt know how to play some version of Soldier's Joy.