Adueñado comes from the verb adueñarse, meaning 'to take possession of' or 'to make something one's own'. It's a less common, more evocative word than simply saying 'you have my feelings'.
In "Motor Y Motivo", the lyrics say, "Te has adueñado de mis sentimientos" (You have taken possession of my feelings). This powerfully conveys how deeply the singer has fallen in love, suggesting a complete and overwhelming capture of their emotions by the beloved. It's a dramatic and memorable way to express profound affection.
The whole song is one man listing what someone has become to him, and he runs out of ordinary nouns almost immediately. "Luz de mis ojos" (Light of my eyes), "Aire que respiro" (Air that I breathe), and then the title arrives: she is his "Motor y motivo" (Driving force and reason). Cumbia reaches for that kind of line all the time, but Grupo 5 keep the images physical instead of floaty. "Dependo de ti como planta a la tierra" (I depend on you like a plant on the soil) is dirt and roots, not a speech about the soul.
The best line is the one that sounds least like a love song. "Ocupas mi mente" (You occupy my mind), "Un noventa por ciento" (Ninety percent of it) is a man doing arithmetic about his own obsession, and generously leaving himself the other ten. By the chorus he has stopped measuring anything: "Y no me cansa decirte te amo" (And I never tire of telling you I love you), then "Le grito al mundo 'te amo, te amo'" (I shout to the world 'I love you, I love you'). What sells it is how little effort any of it took her. "Sin mover un dedo me has hecho adorarte" (Without lifting a finger you have made me adore you) is him admitting she never had to try.