This is the 8188th most frequent Polish word.
olszewski
"Olszewski" is a Polish surname derived from "olsza," meaning "alder tree."
Here, 'Olszewski' is used as a proper noun, representing a surname.
Czy Olszewski jest w pracy?
Is Olszewski at work?
In this sentence, 'Olszewskich' is the plural genitive form referring to the family members of Olszewski.
Historia rodziny Olszewskich jest bardzo interesująca.
The history of the Olszewski family is very interesting.
Here, 'Olszewskiego' is the accusative form, used to indicate the direct object (Mr. Olszewski) of the action 'met' in the sentence.