This is the 6244th most frequent Polish word.
berdiańsku
The word "berdiańsku" is the locative form of "Berdiańsk," referring to the city of Berdyansk, used to indicate location (e.g., "in Berdyansk").
It is used here to indicate the location where the action (working) took place.
Pracowałem w Berdiańsku przez kilka lat.
I worked in Berdyansk for several years.
The word indicates the destination of the action and is part of the locative case.
Przyjechałem do Berdiańska, aby poznać jego historię.
I came to Berdyansk to learn about its history.
The word is used to specify the place related to the action (staying), in the locative case.