Disclaimer: I'm a complete noob about the history of the region and the languages involved.
I just figured out the best way to get an answer on the web is to post a wrong one first, so I went 5 minutes into the subject on Wikipedia and what I've concluded is that maybe it's actually the other way around.
Poland is like "Land of Polans" which were the original tribe of the region.
The Ш letter seems it is a prefix that comes from Hebrew, so maybe, Шпола also refers to Polans in some way.
I must emphasize again that this can be completely wrong.
The name "polans" derives from the word "pole", which simply means "field". There were actually several different groups of Slavs who were known as "polans", all named because of where they settled. One of them did indeed found Poland. But there were also (different) polans in what is now Ukraine - indeed, they were the dominant group, as Kyiv was their city.
In any case, "pol" in the placename can simply refer to a field directly. Or even to something else; in case of Shpola, the local legend is that it was named after the guy who first settled there.