Anhelo comes from the verb anhelar, meaning 'to long for' or 'to yearn for'. It's a strong, poetic word that expresses a deep and intense desire.
In the song, Danny Ocean sings, "Si tú supieras cuánto anhelo tu cuerpo" (If you only knew how much I long for your body). This word perfectly captures the passionate yearning and intense desire the singer feels, making it more impactful than a simpler word like 'quiero' (I want).
Danny Ocean spends two minutes and twenty one seconds on a single idea: he cannot stop thinking about someone, and he never actually tells her. The title says it. "Si tú supieras cuánto anhelo tu cuerpo" (If you knew how much I long for your body) is aimed at a person who apparently has no clue, which is both the joke and the ache of the song. He counts the times he thinks about her, three a night, then the afternoon, then the day. He remembers exactly where things happened, on the boat, in the park.
Then comes the line that makes the song. "Tengo tu panty guardado en mi closet" (I've got your panties tucked away in my closet), and he tells you why he kept it: it still smells like her. It is a bit much, he clearly knows it is a bit much, and he sings it anyway over a beat barely there. The other thread running through it is Brazil. He slips into Portuguese for "Quiero Brasil con você" (I want Brazil with you), admits "Aún me huele a Brasil" (It still smells like Brazil to me), and ends the whole thing on one word, "Carioca" (a girl from Rio), which quietly tells you who she was all along.