in order to understand the title i think is better to read the first sentence: "chi vidde più lieto e felice di me la bella mia donna incontrandomi un dì, mirommi sott'occhio mi disse "zz" ."
this is a kind of old italian language because nowadays we do not use words such as "vidde" or "mirommi". However i try to explain the meaning : the speaker says that nobody can be more happy and glad (lieto e felice) than him when he met his beautiful lover (the female character of the opera). this is a simple explanation, i hope it can help you.
byebye, fede