köken: From Proto-Italic *kalando- (gerundive), from *kalāndo- (gerundive), ultimately from Proto-Indo-European *kelh₁- (“to call, summon, cry out”). The original gerundive form likely meant “[things] which are called out.” When applied to days, the meaning referred to “days which are called out.” The gerundive was then substantivized, eventually coming to refer the first day of a month. Related to…