From Proto-Indo-European *h₂éǵʰ-r̥/n̥- (“day”).
अहर् (ahar) n
- sacrificial or festival day, portion of a sacrifice appointed for one day's performance
- day personified as one of the eight Vasus
- Sir Monier Monier-Williams, A Sanskrit-English dictionary etymologically and philologically arranged with special reference to cognate Indo-European languages, Oxford: Clarendon Press, 1898, page 0124