Iuno

Latin

Juno or Hera Barberini, a 2nd-century statue of the goddess at the Vatican

There are two hypotheses:

From Proto-Indo-European *dyúh₃onh₂-, *dyúh₃nh₂- (“having heavenly authority”), from *dyew- (“sky, heaven”) + *-Hō (“burden, authority”), rendering Iuvō, *Iūnis, normalized to Iūnō, Iūnōnis. See Ancient Greek Διώνη (Diṓnē, “Dione”);
From Proto-Indo-European *h₂yúh₃onh₂-, *h₂yúh₃nh₂- (“the young goddess”), from *h₂óyu (“long time, lifetime”) + *-Hō (“burden, authority”) also rendering *Iuvō, *Iūnis, normalized to Iūnō, Iūnōnis. See Latin iuvenis (“young”).

Iūnō f sg (genitive Iūnōnis); third declension

(Roman mythology, religion) Juno, queen of the gods, patron of rulers and childbirth, equivalent to the Greek Hera.
- 8 CE, Ovid, Fasti VI.283–288:
  cur sit virginibus, quæris, dea culta ministris? / inveniam causas hac quoque parte suas. / ex Ope Iunonem memorant Cereremque creatas / semine Saturni; tertia Vesta fuit. / utraque nupserunt, ambæ peperisse feruntur; / de tribus impatiens restitit una viri.
  Why, you ask, is the goddess tended by virgin ministers? I’ll discover the true causes for this as well. They say that Juno and Ceres were born of Ops by Saturn’s seed; Vesta was the third daughter. The other two married, both reported to have borne children; of the three, one remained who could not bear a husband.
(New Latin) Juno, a Main Belt asteroid.

Third-declension noun, singular only.

Clackson, James, Indo-European Word Formation: Proceedings from the International Conference, 2002

Iuno