Sounding out "jubous," as well as looking at it, I wonder whether it [and possibly juju] might come from dubious. The phrase "I feel jubous" somewhat similar in the essence of its meaning to the description to what "I feel jubous" could mean.

As far as water witching, it works whether you believe or not. I learned it as a surveyor. We used bent welding rods to locate, water supply lines, electrical cables, gas lines and sewers. The key to locating things was simply to know what you are looking for. We were often more accurate than the maps we were working from.