"Lent," c. 1600, from Medieval Latin quadragesima (dies) "the fortieth (day)," altered diminutive of Latin quadrigesimus "fortieth," from quadriginta "forty," related to quattuor "four" (from PIE root *kwetwer- "four"). So called because it lasts forty days. Earlier in English in nativized form Quadragesime (mid-15c.). Related: Quadragesimal. Via the Vulgar Latin form *quaragesima come Old French quaresme, Modern French carême, Spanish cuaresma, Italian quaresima, also ultimately Irish carghas, Gaelic carghus, Welsh garaways.