dyaus

The original meaning of the word is shown in the Sanskrit dyaus, gen. divas, root div, which root appears in an adjective formation as deva, "bright", "heavenly" -- attributes of God -- hence devas, "the bright beings", or, as a noun substantive, dyaus.

The Catholic Encyclopedia, Volume 4: Clandestinity-Diocesan Chancery 1840-1916 1913

In its substantive form, dyaus is either masculine e.g. "heaven", "sky" -- or feminine, as Heaven (personified).

The Catholic Encyclopedia, Volume 4: Clandestinity-Diocesan Chancery 1840-1916 1913

Indo-Iranian deva, Sanskrit dyaus (gen. divas), Latin deus, Greek theos, Irish and Gaelic dia, all of which are generic names; also

The Catholic Encyclopedia, Volume 6: Fathers of the Church-Gregory XI 1840-1916 1913

If this root was first used actively for the act of shedding light, of striking a spark, of shining, it was a step farther to transfer this originally active root to the image which the sky produces in us, and to call it a “shiner,” _dyu_ (nom. _dyaus_), and then with a new upward tendency to call all bright and shining beings, _deva_, _deus_.

The Silesian Horseherd - Questions of the Hour 1861

And yet there's also the example of *dyēus 'sky' (confirmed by Sanskrit dyaus which, if the stem vowel were short, would presumably have become *dyos1) and even though one might argue that the reconstructed accusative form *dyēm ( Sanskrit dyām) could likely derive from earlier *dyēum just as well as *dyeum, the genitive form *diwós shows that the underlying vowel can only be short *e by all the normal rules of PIE ablaut (i.e. long *ē alternates with short *e while short *e alternates with zerograde).

Archive 2008-06-01 2008

And yet there's also the example of *dyēus 'sky' (confirmed by Sanskrit dyaus which, if the stem vowel were short, would presumably have become *dyos1) and even though one might argue that the reconstructed accusative form *dyēm ( Sanskrit dyām) could likely derive from earlier *dyēum just as well as *dyeum, the genitive form *diwós shows that the underlying vowel can only be short *e by all the normal rules of PIE ablaut (i.e. long *ē alternates with short *e while short *e alternates with zerograde).

Nominative Lengthening and a reinterpretation of Szemerenyi's Law 2008

_dyaus_ in Sanskrit is the name of the sky, if used as a feminine; if used as a masculine, as it is still in the Veda, it is the sky as a man or as a god — it is Zeus, the father of gods and men.

Chips From A German Workshop, Vol. V. Miscellaneous Later Essays 1861