This is the 6353rd most frequent Polish word.
brzeźnickiej
"Brzeźnickiej" is the genitive or locative form of "Brzeźnicka," which refers to something or someone related to Brzeźnica, a place in Poland. It can also denote a street name, meaning "of Brzeźnicka."
The word 'Brzeźnickiej' refers to the name of the street, indicating a locative case usage in context of address.
Mieszkałem kiedyś przy ulicy Brzeźnickiej.
I used to live on Brzeźnicka Street.
Here, 'Brzeźnickiej' functions as an adjective modifying 'Library', implying possession or association.
Książka została znaleziona w bibliotece Brzeźnickiej.
The book was found in the Brzeźnicka Library.
In this instance, 'Brzeźnickiej' describes a road in genitive case, showing relation or attribution.