This is the 9609th most frequent Russian word.
хозяину
"Хозяину" means "to the owner" or "to the master" in English.
The word 'хозяину' is used as a dative case noun indicating the indirect object receiving the letter in the sentence.
Я отдал письмо хозяину дома.
I handed the letter to the owner of the house.
Here, 'хозяину' is in the dative case, showing the person to whom the subject is approaching to initiate a discussion.
Я подошёл к хозяину кафе, чтобы поговорить.
I approached the owner of the cafe to talk.
In this sentence, 'хозяину' is used in the dative case to indicate the recipient of the keys.