Etymology Dictionary

QUARANTINE,  a space of forty days.  (F.,—L.)   Spelt quarentine in Minsheu, who gives it the old legal sense, viz. a space of forty days during which a widow might dwell unmolested in her husband's house after his decease.   Blount gives this form and sense, and derives it from O.F. quarantine.   He also gives quarantain, meaning (1) Lent, (2) a forty days' truce or indulgence, (3) 'the forty days which a merchant, coming from an infected port, stays on shipboard for clearing himself;' the last sense being the usual one in mod. E.—O.F. quarantine (Roquefort), usually quarantaine, 'Lent, a term of forty days,' &c.; Cot.—Low Lat. quarantina*, quarantana*, quarentena* (all of which prob. were in use, though Ducange only mentions quarantenum), a space of forty days, formed as if from quaranta*, forty, answering to F. quarante; this quaranta being nothing but a shortened form of Lat. quadraginta, forty.   See Quadragesima.   Cf. Ital. quaranta, forty; fare la quarantana, 'to keepe lent,... to keepe fortie days from company, namely if one come from infected places, as they vse in Italy;' Florio.   Thus the mod. sense seems to be of Ital. origin.