This is the 12729th most frequent Turkish word.
isimlerinin
"Of their names"
The word 'isimlerinin' is used to indicate possession, referring to 'names' belonging to 'books'.
Kitapların isimlerinin ne olduğunu soruyordu.
He was asking what the names of the books were.
Here, 'isimlerinin' denotes names that belong to 'students'.
Öğrencilerin isimlerinin listesini hazırladık.
We prepared a list of the students' names.
In this sentence, 'isimlerinin' is used in the context of ownership, describing names belonging to 'animals'.