Caligo translates to "fog" or "mist". It's a less common and more evocative word than the everyday "nebbia" for fog, giving it a poetic and slightly mysterious feel.
In the song, Bresh uses it to describe the atmosphere of his neighborhood, singing "Caligo sulla zona, morivamo di noia" (Fog over the area, we were dying of boredom). This imagery suggests a sense of stagnation or a hazy, perhaps melancholic, memory of his youth, making it a unique and memorable choice.
Bresh spends this whole song in one Genoa neighbourhood, and he dates it with objects rather than years: "Fuori dalla mia scuola suonava il Motorola" (Outside my school the Motorola was ringing), helmets carried around by hand, music coming out of a phone speaker. The mood underneath it is boredom, said outright in "Caligo sulla zona, morivamo di noia" (Fog over the neighbourhood, we were dying of boredom). Caligo is the Genoese word for the sea fog that sits on the city, and reaching for it instead of the standard Italian is the point: this is one specific place, not a generic hometown.
The hook is someone at the door who will not go away. "Dai, che fai? Ti attacchi al campanello, dimmi, dai, cos'hai?" (Come on, what are you doing? You lean on the doorbell, tell me, come on, what's wrong?) is the sound of being pulled out of the house, and the chorus follows that noise into the street, through a window and onto a piano until morning. The details stay small and physical, like "Sono a Quinto tra i sassi e io non ho niente per stendermi" (I'm in Quinto among the rocks and I've got nothing to lie down on), a real stretch of rocky Genoese shoreline rather than a beach. By the last verse he is totting up what the years cost him: "Sono cambiato per i soldi, ma non credo, no" (I changed because of the money, but I don't think so, no). He does not sound entirely sure.