As a Scout leader and long time camper, I've taken my share of "dumps in the woods", but never have I heard of a "jungie".
I like slang, and the language it is from is unimportant to me. However, learning obscure slang that I will never use (or probably never use) seems like a waste of time and energy. There are plenty of words in "standard" Swahili, Tibetian, Ukranian or whatever that I don't know but should learn. And so it is with English, be it British, American, or whatever. Aren't there better ways to spend time? Just a thought. I got to go talk to a man about a horse.