This is the 14177th most frequent Polish word.
prawnikowi
"To the lawyer" (dative form of "prawnik").
The word 'prawnikowi' is the dative form of 'prawnik', used here to indicate the person receiving thanks (indirect object).
Dziękuję prawnikowi za pomoc.
I thank the lawyer for the help.
Here, 'prawnikowi' signifies the recipient of the book, showing its function as a dative form in Polish.
Zabrałem książkę od prawnika i podałem prawnikowi.
I took the book from the lawyer and handed it to another lawyer.
In this sentence, 'prawnikowi' follows the verb 'ufam', which governs the dative case for indicating the person to whom trust is directed.