"Sa' ghaH loDnI'wI''e'. martaq 'oH pongDaj'e'. DaSov'a'?"
Translation:My brother is a general. His name is Martok. Do you know him?
It marks the explicit subject referred to by the pronoun acting as verb.
Let's look at another type of Klingon sentence. 'IH pongDaj means, "His name is beautiful." 'IH 'oH means, "It is beautiful." We cannot use both 'oH and pongDaj even though they refer to the same thing (or maybe because they refer to the same thing). We have to choose whether we want to be explicit and state the subject or whether we want to use a pronoun and hope our audience will know what we are referring to.
In a "to be" sentence where we equate two nouns instead of using a verbal adjective (like 'IH), we have to use the pronoun like it was a verb. But it doesn't stop also being a pronoun. So, mataq 'oH is a complete sentence meaning, "It is Martok." But if we want to explicitly state the pronoun, we can't substitute pongDaj in place of 'oH the way we did in the other sentence. But we are also not allowed to just put the two words next to each other. We have to somehow mark the of grammaticality of this construction. So we use the focus/emphasis marker to add on the duplicate subject. Thus, martaq 'oH pongDaj'e' winds up saying something similar to, "It is Martok, I'm talking about his name."