This is the 6098th most frequent Polish word.
andrzejowi
"Andrzejowi" is the dative case of "Andrzej," meaning "to Andrzej" or "for Andrzej."
Here, 'Andrzejowi' is in the dative case, which is used for indirect objects or recipients in Polish language grammar.
Dziękuję Andrzejowi za pomoc.
Thank you Andrzej for your help.
In this sentence, 'Andrzejowi' again is in the dative case, marking Andrzej as the recipient of the action.
Podarowałem książkę Andrzejowi na urodziny.
I gave a book to Andrzej for his birthday.
Here 'Andrzejowi' is dative used to indicate that Andrzej is the one being addressed or spoken to.