Appias is a water nymph in Roman myth, the Goddess of the Appian Spring or Fountain located in front of the temple of Venus Genetrix in the Julian Forum in Rome. This fountain was surrounded by statues of nymphs who were collectively called the Appiades, and in modern times such statues have been found in the area where the well was.

Nymphs are invariably female, and represent the creative powers of nature: the idea of nymphs comes from the Greeks, who had different kinds for all sorts of natural things like trees, mountains and groves as well as springs. Water nymphs guard springs, places that represent the connection between the Underworld and ours, and they are often connected with prophecy.

The name Appias is a bit of a puzzle. At first glance it would seem to be related to some famous landmarks of ancient Rome such as the Via Appia, the most famous of the roads from Rome, or the Aqua Appia, the first aqueduct built to supply water to Rome. But both of those are named for the censor Appius Cladius Caecus, who was responsible for having them built in the 4th century BCE. The springs that fed the aqueduct were nameless as far as I've been able to find, and at any rate weren't in Rome itself; and the fountain of Appias in Rome was not supplied with water from the Aqua Appia anyway, as the aqueduct did not service that part of Rome. And the name "Appius" is of unknown origin and it is not known what it meant, so there's no help there.

I would guess that the fountain or well of Appias was a genuine spring and not aqueduct fed, since a natural spring is possessed of the numinous or magical quality that leads to a divinity being personified as its spirit. The statues of the Appiades were apparently fairly famous; Pliny in his Natural History says that one Asinius Pollio had a statue of them by Stephanus, which is taken to be a copy of the ones by the temple of Venus. However, this same group by Stephanus is sometimes called the Hippiades, which would relate it to horses.

The Romen poet Ovid, in his Ars Amatoria ("The Art of Love", perhaps the first banned book in history) uses the term appiades to refer to prostitutes of that neighborhood in Rome by the spring of Appias.