Diespiter.

Old Latin from Proto-Italic *djous patēr (“Jupiter”, literally “Sky Father”) from *djous + *patēr, from Proto-Indo-European *dyḗws (“sky god”, literally “the bright one”) from *dyew- (“to be bright, day sky”) + *ph₂tḗr (“father”). Essentially equivalent to diēs + pater; adds the title “Father” to Old Latin Diovis (“Jove”) whence the oblique cases of later forms of Diēspiter are derived by analogous formation (cf. Iuppiter, Iovis). Cognate of Umbrian 𐌉𐌖𐌐𐌀𐌕𐌄𐌓 (iupater); Sanskrit द्यौष्पितृ (Dyáuṣpitṛ́). Related by prime root to Diāna, dīvus, deus, and Ancient Greek Ζεύς (Zeús)—the Greek god to whom Roman Diēspiter is later equated—compare the equivalent vocative phrase in Doric Greek Δεῦ πάτερ (Deû páter), Attic Greek Ζεῦ πάτερ (Zeû páter, “O father Zeus”).