The name Voevodksy comes from two old russian words: vodit, which means "to lead", and voena which means war. So, voevod, would mean something like "war leader", or general. (Source: russian friend that I just consulted.)
To make things even more interesting, Poland is actually divided in regions / provinces called "województwa" (plural), or literally "lands that belong to the wojewoda". A "województwo" (singular) is more or less the equivalent of a German "Land" or US American "states".
For instance, the Voevoda of Defense (modern minister of defense?) would figure out how to fortify and defend a city from assault. Similarly, a Reconnaissance Voevoda would be sent to figure out the position and the size of an enemy. So it's not necessarily the general, although it looks like the highest class of Voevoda "Bolshoi Voevoda" or "Big Voevoda" could probably be compared to modern day Generals. I'm not entirely sure if one could progress up the ranks or if they just sort of branched out. Very interesting read here (in Russian) [1]
In Ancient Rus, it was strictly a military rank, and simply meant "general" (or something roughly equivalent - a commander of a large military force, at the level where large-scale strategic considerations are as important as battlefield tactics).
That word "voevoda" existed before Russians were even a thing.