HYLLOS (Hyllus) was a giant of Lydia in western Anatolia for whom the river Hyllos was named.
GAIA (Pausanias 1.35.7)
HYLLUS (Hullos). A son of Ge, from whom the river Hyllus in Lydia was believed to have derived its name. His gigantic bones were shown in Lydia at a very late period. (Paus. i. 35. in fin.)
Source: Dictionary of Greek and Roman Biography and Mythology.
CLASSICAL LITERATURE QUOTES
Pausanias, Description of Greece 1. 35. 7 - 8 (trans. Jones) (Greek travelogue C2nd A.D.) :
"But what really caused me surprise is this. There is a small city of upper Lydia called The Doors of Temenos. There a crest broke away in a storm, and there appeared bones the shape of which led one to suppose that they were human, but from their size one would never have thought it. At once the story spread among the multitude that it was the corpse of Geryon, the son of Khrysaor (Chrysaor), and that the seat also was his. For there is a man's seat carved on a rocky spur of the mountain. And a torrent they called the river Okeanos (Oceanus), and they said that men ploughing met with the horns of cattle, for the story is that Geryon reared excellent cows.
And when I criticized the account and pointed out to them that Geryon is at Gadeira, where there is, not his tomb, but a tree showing different shapes, the guides of the Lydians related the true story, that the corpse is that of Hyllos (Hyllus), a son of Ge (the Earth), from whom the river is named. They also said that Herakles (Heracles) from his sojourning with Omphale called his son Hyllos after the river."
- Pausanias, Description of Greece - Greek Travelogue C2nd A.D.