Uhmmm this sounds like a really mashed-up mess here. "Besame" = "kiss me" in Spanish. This is a pretty well-known expression from the classic song "Bésame Mucho". "il bucho" = err, this doesn't make much sense. I guess it's a joke, as if you meant to say "mouth" (la bocca), but instead say something more like "hole" (il buco). So in a squashed up way, you're saying "kiss me (on?) the hole", but half-sounding like the song "Bésame Mucho". Does that make sense? Any other theories? :)

Finally, he revealed that its meaning--kiss asshole. Gracias!