conc▪ denom. from karantīnaẗ ‘quarantine’, from Fr quarantaine ‘id.’, deriv. from quarante ‘forty’, from Lat quadraginta ‘forty’, lit. *‘four tens’, composed of quadra-, der. from quattuor ‘four’, and ginta, der. from decem ‘ten’, IE *kʷetwer + *dekm – Rolland2014. »The name is from the Venetian policy (first enforced in 1377) of keeping ships from plague-stricken countries waiting off its port for 40 days to assure that no latent cases were aboard« (EtymOnline, s.v. quarantine).