Early 17th century. From Italian quarantore, plural noun (although this is apparently first attested later: 1664 as †quarant'hore; also quarant' ore) from quaranta forty + ore, plural of ora.
Definition of Quarant' Ore in US English:
Quarant' Ore
(also Quarantore, Quarantor)
noun
= the forty hours.
Origin
Early 17th century. From Italian quarantore, plural noun (although this is apparently first attested later: 1664 as † quarant'hore; also quarant' ore) from quaranta forty + ore, plural of ora.