This is the 8973rd most frequent Polish word.
sobieski
"Sobieski" is a Polish surname, most notably associated with King Jan III Sobieski of Poland.
The word 'Sobieski' is used here as a proper noun, referring to Jan III Sobieski, the historical figure and king of Poland.
Sobieski był znanym królem Polski.
Sobieski was a famous king of Poland.
In this sentence, 'Sobieski' refers again to Jan III Sobieski, connecting to his commemoration via the monument dedicated to him.
W parku widziałem pomnik Sobieskiego.
In the park, I saw a monument of Sobieski.
Here, 'Sobieski' is used as part of the name of a street, implying the street is named in honor of Jan III Sobieski or his lineage.