Desenamores comes from the verb desenamorarse, which means "to fall out of love". It's the direct opposite of the more common verb enamorarse (to fall in love), created simply by adding the prefix des-, which reverses the meaning.
In the song's outro, J Balvin says he made this ballad "pa' que te enamores o te desenamores" (so you can fall in love or fall out of love). This clever wordplay captures the bittersweet reality that a song can be the soundtrack for both the beginning and the end of a romance, making this a uniquely powerful and memorable word to learn.
J Balvin and Jay Wheeler are going through it in this song. It's all about a super messy, on-again, off-again relationship where nobody knows what's happening. One minute he's begging her to make a decision: "Dime si te vas, pa' emborracharme de una vez por todas" (Tell me if you're leaving, so I can get drunk once and for all). He's so full of jealousy and frustration that he says because of her, he "descubrí que los hombres sí lloran" (discovered that men do cry).
He knows the whole situation is a toxic cycle. They fight, she threatens to leave, and then she comes back. He admits, "Sé que vas a pedirme volver otra vez / Y yo, de pendejo, digo sí otra vez" (I know you're going to ask me to come back again / And I, like an idiot, say yes again). Even though he knows they're "nada serio" (nothing serious), he can't help his feelings. It's a classic case of someone driving you crazy, but you just don't want to lose them.