Debilitan comes from the verb debilitar, meaning "to weaken" or "to debilitate". It's a strong and evocative word that goes beyond simple affection.
In the song, the singer uses it to express how the object of his affection's charm and beauty are so overwhelming that they literally "weaken" him. This dramatic phrasing highlights the intensity of his feelings, making it a memorable and impactful word choice.
La Fiera De Ojinaga's "Eres Tan Bonita" is a super sweet and direct declaration of love! The singer is completely smitten, telling this "chiquita bonita" [pretty little girl] that she's constantly on his mind. He's addicted to kissing her lips, saying "se me hizo vicio besar tu boquita" [it became a vice to kiss your little mouth], and he's totally weakened by her.
He's captivated by her smile and her eyes, which he says "me paralizan" [paralyze me]. It's an addiction he can't get rid of, making him want her "por siempre cerquita" [forever close]. He's not just thinking about her casually; he's thinking about a serious future, wanting their relationship to stop being a mystery. He even says, "por tu amor yo voy al infinito y vuelvo" [for your love I go to infinity and come back], showing how deeply he cares and how sure he is about wanting her to be his and him to be hers.