If Dorlas were an Elvish name, it would seem to translate as something like 'land leaf', which could be taken as a reference to Dorlas' forest home. However, it seems more likely that the name comes from the Mannish language of the Haladin, and is not therefore interpretable.
2
Dorlas' son Avranc is not named in the canonical texts, but he does appear in the tale of The Wanderings of Húrin in volume XI of The History of Middle-earth.