This is the 8835th most frequent Russian word.
потапа
"Потапа" is not a standalone Russian word but may be a proper name (Potapa). If additional context clarifies its meaning, let me know.
Here, 'Потапа' is used as a proper noun referring to a person's name in the accusative case, denoting the subject of the action of coming home.
Когда Потапа пришёл домой, он был уставшим.
When Potapa came home, he was tired.
In this sentence, 'Потапа' is again a proper noun used in the accusative case, referring to the direct object of the verb 'зовут' (call).
Дети зовут своего друга Потапа гулять.
The children call their friend Potapa to go for a walk.
Here, 'Потапа' is in the accusative case, referring to the individual being remembered.