This is the 6978th most frequent Russian word.
арсения
"Арсения" is a Russian female name, derived from the Greek name "Arsenios," meaning "virile" or "strong."
Here, 'Арсения' is a proper noun, a name, used as the subject of the sentence indicating who performed the action of meeting.
Арсения встретила нас возле парка.
Arsenia met us by the park.
In this sentence, 'Арсении' is in the genitive case, denoting possession, indicating that the books belong to Arsenia.
Мы поговорили о книгах Арсении.
We talked about Arsenia's books.
'Арсению' here is the name 'Арсения' in the accusative case, used to denote the object of the action of the verb 'пригласил'. The name refers to the person being invited.