It wasn't penned as a romantic farewell, but "Bella Ciao" meaning "goodbye beautiful" in Italian is a song that has come to symbolize a parting with oppression. When the phrase was discovered etched on an unspent bullet casing linked to the man accused of killing conservative US activist Charlie Kirk, it wasn't just some cryptic clue. It was a refrain bearing history, drawn from a century-old Italian protest song, which has long been a global tune of resistance.