When Xenophon reaches Pontic region there he mentions Drilae.

 When Xenophon reaches Pontic region there he mentions Drilae. A small tribe dwelling near Trabzon. Not much is known about this tribe. Later it is mentioned few times as Drillae/Driloi or one time as Dryloi. 

Hewsen tentatively ( with question mark ) link the names of Daranali and Derjan to this Drilae but this is a weak theory. He also see a link with Trel-k' which is much more robust.

Trelk' is the Armenian name of Trialeti ( a region in Georgia ) with the -k' plural suffix. It is quite possible that those Drilae were an offshoot of Trelk' who moved to Pontic region under the pressure of Cimmerians or due other event.

Why I think Cimmerians? Because Strabo mentions numerous times a tribe known as Treres, which was either a Thracian or Cimmerian tribe. He mentions it both in West and East of Black sea. Once more we see mysterious Thracians in or around Armenia. Which means that the term Thracian was used as catch all term for tribes that Greeks had hard time to classify.

It is quite possible that the early form of Drilae/Trel-k' was initially Trer-. Later a shift occured. Pliny's term Triare seems to support this assumption.

Wether those Treres/Treles came in Iron Age or they were present in SW Georgia since Bronze Age is hard to say. But some of them ultimately moved to Pontic region ( with Qulha? ) where they were mentioned by Xenophon.

http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0202:book=5:chapter=2&highlight=drilae

http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0064:entry=treres-geo