This is the 6112th most frequent Polish word.
antka
"Antka" is the genitive or accusative singular form of "Antek," a diminutive of the Polish name Antoni.
'Antka' is the accusative case for the masculine, informal name 'Antek', used for a direct object in the sentence.
Wczoraj widziałem Antka w parku.
Yesterday, I saw Antek in the park.
'Antka' here is used in the genitive case, indicating possession, meaning 'of Antek'.
Nie mam książki Antka.
I don't have Antek's book.
'Antkowi' is the dative case form of 'Antek', indicating the indirect object of the action.