Vocative

In Latin, there are six cases: nominative, genitive, dative, accusative, ablative, and vocative.

The vocative is the case we use when we call or address someone or something.

In English, the vocative may be indicated by an addressee–address separation comma, or by the particle O, as in "What is the matter, sir?", "Mother, listen!", or "O Lord".

[T]he two latter will hardly come neither, if they think it will be to hear your whining vocatives.