It’s not surprising that the word quarantine originated in Venice. The concept of quarantena, meaning a duration of forty days, was exactly how long medieval Venetian authorities felt was sufficient to figure out whether or not a ship–or a person–might infect someone else with bubonic plague.
Venice is not a land mass at all, but rather a cluster of hundreds of islands. Some are connected by bridges, but many stand lonely in the Venetian lagoon. It’s these islands where Venetian authorities began to send citizens who developed the tell-tale signs of plague.
The Lazzaretto Vecchio was established around 1400 on a small island off just beyond the Lido of Venice.