English 'quarantine' descends from Italian 'quarantina' (forty days), a term born in Venice's 14th-century plague controls — the forty-day isolation period carried both practical and biblical weight, the number forty being the traditional duration of purification and trial.
A state, period, or place of isolation in which people or animals that have arrived from elsewhere or been exposed to infectious disease are placed.
From Italian 'quarantina' or 'quarantina giorni' (forty days), from 'quaranta' (forty), from Latin 'quadrāgintā' (forty), from PIE *kʷetwer- (four) + a decimal suffix. The word arose directly from Venetian public health practice: ships arriving in Venice during plague outbreaks were required to anchor offshore for forty days before passengers could disembark. The number forty was deeply symbolic in Christian and classical tradition — Moses spent forty days on Sinai, Jesus forty days in the desert, Noah's flood lasted
The forty-day period of quarantine was not chosen for epidemiological reasons — germ theory was centuries away. It was chosen because forty was the biblical number of trial and purification: forty days of flood, forty years in the desert, forty days of fasting. Venice accidentally chose a symbolically resonant period that happened to exceed