Macrobius, Saturnalia 1.7:
“When Janus first stamped images onto bronze coins, he maintained his reverence to Saturn to such a degree that, since he had come to Italy by boat, one side of the coin would show an image of his head, while the other side displayed a ship; in this way he propagated Saturn’s memory for future generations. Copper thus marked is even today understood to apply to dice games, when boys throwing their coins into the air playfully exlaim ‘heads or ships’ as a testament to the practice’s antiquity. Most agree that Janus and Saturn ruled together in peace and founded neighboring towns with communal labor, excepting the claims of Vergil who writes,
This spot was given the name of Janiculum, and that one was given the name Saturnian
It also comes to mind that later generations dedicated two successive months to them, as December is sacred to Saturn, while January bears the name of Janus. When amidst all of this Saturn suddenly disappeared from notice, Janus contrived some augmentation of his honors. First, he named all of the land which obeyed his decree ‘Saturnia.’ Then he established an altar with sacred rites to Saturn as though to a god, which he called ‘Saturnalia.’ By so many generations do the Saturnalia precede the age of Rome herself! He then ordered him to be revered with the majesty of religion as the author of a better life for humans. His statue serves as a sign of this: he added to it a scythe, that symbol of the harvest.
Cum primus quoque aera signaret, servavit et in hoc Saturni reverentiam, ut, quoniam ille navi fuerat advectus, ex una quidem parte sui capitis effigies, ex altera vero navis exprimeretur, quo Saturni memoriam in posteros propagaret. Aes ita fuisse signatum hodieque intellegitur in aleae lusum, cum pueri denarios in sublime iactantes capita aut navia lusu teste vetustatis exclamant. 23 Hos una concordesque regnasse vicinaque oppida communi opera condidisse praeter Maronem, qui refert:
Ianiculum huic, illi fuerat Saturnia nomen,
etiam illud in promptu est, quod posteri quoque duos eis continuos menses dicarunt, ut December sacrum Saturni, Ianuarius alterius vocabulum possideret. 24 Cum inter haec subito Saturnus non conparuisset, excogitavit Ianus honorum eius augmenta. Ac primum terram omnem ditioni suae parentem Saturniam nominavit: aram deinde cum sacris tamquam deo condidit, quae Saturnalia nominavit. Tot seculis Saturnalia praecedunt Romanae urbis aetatem. Observari igitur eum iussit maiestate religionis quasi vitae melioris auctorem: simulacrum eius indicio est, cui falcem, insigne messis, adiecit.