This is the 11182nd most frequent Russian word.
грецких
"Грецких" is the genitive plural form of "грецкий," meaning "of Greek" or "Greek" in certain contexts, often referring to "walnuts."
Here, 'грецких' is an adjective in plural genitive form describing 'орехов' (walnuts), indicating possession or origin.
У нас в саду растёт несколько грецких орехов.
We have several walnut trees growing in our garden.
In this context, 'грецких' is an adjective in plural genitive form describing 'государств' (states), referring to geographical or cultural origin.
В книге была упомянута история грецких государств.
The history of Greek states was mentioned in the book.
Here, 'грецких' again is an adjective agreeing with the noun 'орехов' (walnuts), used to specify the type of nuts.