"OK, Mike -- you got THREE valid answers. (Highway pots, orchard protection and wartime smoke generators)"
OK, I've already answered that in a previous message.
"The reason I was asking is that my brother and sister in law have a set (the green & red ones you find on Google) that they're using for bug lamps.
I went to their place for a BBQ, saw them, and asked where they got the smudge pots. A bunch of the younger people there looked at us as if we were insane -- they had no idea that anything existed before blinking lights."
As for the military smoke generator, I really think that's an aside answer. It's likely that the military smoke generators got that nickname when people who were familiar with the agricultural and construction smudge pots joined the military in WW II. Military smoke generators of that era normally worked by squirting raw fuel on a hot surface, like the exhaust.