This is the 2749th most frequent Russian word.
ирины
"Iрины" is the plural form of the name "Ирина" (Irina), which is a Russian feminine given name equivalent to "Irene" in English.
The word 'Ирины' here indicates possession, showing whom the books belong to.
Это книги Ирины.
These are Irina's books.
In this case 'Ирины' specifies the author of the poems, emphasizing them as a creation of hers.
Я видел стихи Ирины.
I saw Irina's poems.
The usage here implies the context or scope of discussion is related to Irina and her experiences.