Cobarde translates to "coward" in English. It's a strong, emotionally charged word that isn't used lightly, making it stand out in the lyrics.
In "Tragos Amargos," the singer uses this word to describe himself, admitting, "Y me siento como un cobarde que hasta me pongo a llorar" (And I feel like such a coward that I even start to cry). This raw self-reflection about his heartbreak and vulnerability makes the word particularly impactful and memorable within the song's narrative.
Tragos Amargos is about drinking to forget someone, and finding out that it does not work.
The singer is alone in a corner of a bar, and he reaches for the same word to describe himself that he uses for what she did to him. He is nailed to that spot the way she nailed his heart. The drinks in front of him are not comfort. He says plainly that they are pure sadness, and that they are his pain.
He never finds out why she left. What he holds on to instead is what he is still sure of: that she loved him, that she adored him. So he leaves the door open. If she ever wants to come back, he will be waiting.
The chorus is where the title lands. The bitter liquor does not make him forget, and saying that out loud leaves him feeling like a coward, because it brings him to tears. That small, honest turn is the whole song. The drink was supposed to be the cure, and all it does is make the feeling louder.