The problem, for many is that Polish entails a plethora or variant forms for many things* including the patronymic nickname indicating who one's father was.
The adjectival -ski ending was usually toponymic (from a localtiy) but could also have originated as a patronymic nick as in Kowalski (młot kowalski and Jan Kowlaski - a blacksmith's hammer and John the blacksmith's son).
Less common patronymic endings include: -czyk, -ek, -ik and -yk.
It is important to remember that the origin of these nicknames-turned-surnames goes back many centuries and has nothing to do with anyone's known ancestors, unless you know your family line back to the 14th or at least 18th century.
* There exist numerous forms for many Polish diminutives, eg: from pies (dog) - piesek, pieseczek, piesio, psina, psinka, psiaczek and also an augmentative form: psisko (big, old cur).
By contrast, from the basic root dog English has only the one form: doggie. There are of course non-dog-rooted synonyms such as cur, mutt, canine, mongrel and Heinz 57.
