An Etymological Dictionary of Astronomy and Astrophysics

Relating to or occurring at sunset. → heliacal

Etymology (EN): Acronical, from Gk. akronukos, from akros
“tip, end,” cf. Av. aγra- “top, first,” Skt. agra- “first, foremost, climax”

• nuks, nuktos “night,” → night.

Etymology (PE): Šâmgâhi, adj. of šâmgâh “evening,” from šâm “evening, evening meal” + gâh “time.” The first component, šâm, from Mid.Pers. šâm “evening meal, supper,” from Av. xšāfnya- “evening meal,” from Av. xšap-, xšapā-, xšapan-, xšafn- “night” (O.Pers. xšap- “night,” Mid.Pers. šap, Mod.Pers. šab “night”); cf. Skt. ksap- “nigh, darkness;” Hittite ispant- “night.” The second component gâh “time,” Mid.Pers. gâh, gâs “time,”
O.Pers. gāθu-, Av. gātav-, gātu- “place, throne, spot;” cf. Skt. gâtu- “going, motion; free space for moving; place of abode;” PIE *gwem- “to go, come.”