The Professor reveals that his grandfather, who fought in the Italian resistance, taught him the song. This establishes a lineage of rebellion that justifies the heist in his mind as a moral act rather than a criminal one.
: Una mattina mi sono alzato, O bella ciao, bella ciao, bella ciao, ciao, ciao, Una mattina mi sono alzato, E ho trovato l'invasor. La Casa De Papel - Bella Ciao [Lyrics] (Money Heist)
Originally, "Bella Ciao" was used by the Italian anti-fascist resistance during World War II. Its lyrics tell the story of a partisan who wakes up to find an invader and chooses to die for freedom. By incorporating this history, the show frames the Professor and his crew not as mere thieves, but as "partisans" fighting a modern "invader"—the oppressive banking system. Symbolism in the Series The Professor reveals that his grandfather, who fought