Camelot refers to a hawker or street vendor, someone who sells goods, often with a bit of showmanship, in public places.
In the song, Aznavour paints a picture of his city's sounds, and the "camelot bon enfant" (good-natured hawker) is one of the distinct voices. It's an interesting word because it evokes a specific, lively urban scene that might be less common in everyday conversation, making it memorable and unique to the song's theme of city life.
Aznavour builds this song out of the sounds of a city street: the rag collector's call, the chestnut seller's cry, a traffic officer waving pedestrians on, newspaper vendors shouting the headlines, a market trader hawking ties. Each one gets its own little verse, like a snapshot of a passing character.
Between them, the song keeps returning to the same quiet line: his mind, riding along on a train, keeps drifting back to all these familiar cries. The city's noise becomes memory rather than noise — the sound of home.
Near the end, the mood shifts. Among all the street vendors, there's a couple parting on a station platform, one asking the other to write. It's a small, tender moment tucked between all the shouting, and it's what the whole song has been quietly building toward: these cries are what "home" sounds like, whether they're funny, ordinary, or heartbreaking.