It's a bundle in Ukrainian. You know, like in cartoons when a character walks away sadly with a bundle on a stick. I have a vivid childhood memory of a scene in Tom & Jerry where Tom does this. The idea of backed up files being in a digital bundle on a digital stick amused me enough to name the program like this.

I can't comment on the Ukrainian word, but the "hobo sack" bundle-on-a-stick you're talking about is specifically called a "bindle":

https://en.wikipedia.org/wiki/Bindle