Sol vel quod ita Sabini, vel quod solus ita lucet, ut ex eo deo dies sit. luna, vel quod sola lucet noctu. itaque ea dicta Noctiluca in Palatio: nam ibi noctu lucet templum. hanc ut Solem Apollinem quidam Dianam vocant; Apollinis vocabulum graecum alterum, alterum latinum), et hinc quod luna in altitudinem et latitudinem simul it, Diviana, appellata. hinc Epicharmus Ennii Proserpinam quoque appellat, quod solet esse sub terris. dicta Proserpina, quod haec ut serpens modo in dexteram modo in sinisteram partem late movetur. serpere et proserpere idem dicebant, ut Plautus
quod scribit: ‘quasi proserpens bestia’ [Poen. 1034, Stich. 724]. quae ideo quoque videtur ab Latinis Iuno Lucina dicta vel quod est et terra, ut physici dicunt, et lucet; vel quod ab luce eius, qua quis conceptus est, usque ad eam, qua partus quis in lucem, luna iuvat, donec mensibus actis produxit in lucem, ficta ab iuvando et luce Iuno Lucina. a quo parientes eam invocant: luna enim nascentium dux, quod menses huius. hoc vidisse antiquas apparet, quod mulieres potissimum supercilia sua attribuerunt ei deae. hic enim debuit maxime collocari Iuno Lucina, ubi ab diis lux datur oculis.
(Varro, De Lingua Latina 5.68-69)
Sol ‘Sun’ is so named either because the Sabines called him thus, or because he solus ‘alone’ shines in such a way that from this god there is the daylight. Luna ‘Moon’ is so named certainly because she alone ‘lucet‘ shines at night. Therefore she is called Noctiluca ‘Night-Shiner’ on the Palatine; for there her temple noctu lucet ‘shines by night.’ Certain persons call her Diana, just as they call the Sun Apollo (the one name, that of Apollo, is Greek, the other Latin); and from the fact that the Moon goes both high and widely, she is called Diviana. From the fact that the Moon is wont to be under the lands as well as over them, Ennius’s Epicharmus calls her Proserpina. Proserpina received her name because she, like a serpens ‘creeper,’ moves widely now to the right, now to the left. Serpere ‘to creep’ and proserpere ‘to creep forward’ meant the same thing, as Plautus means in what he writes: ‘Like a forward-creeping beast.’ She appears therefore to be called by the Latins also Juno Lucina, either because she is also the Earth, as the natural scientists say, and lucet ‘shines’; or because from that light of hers in which a conception takes place until that one in which there is a birth into the light, the Moon continues to help, until she has brought it forth into the light when the months are past, the name Juno Lucina was made from iuvare ‘to help’ and lux ‘light.’ From this fact women in child-birth invoke her; for the Moon is the guide of those that are born, since the months belong to her. It is clear that the women of olden times observed this, because women have given this goddess credit notably for their eyebrows. For Juno Lucina ought especially to be established in places where the gods give light to our eyes. (tr. Roland G. Kent)