Origins and possible affiliation of Mardes.
One of first mentions of Mardes in Armenia is from Xenophon's Anabasis. They are mentioned in the Orontid's army alongside Armenians and Chaldes. Chaldes are those related to Khaltik' and should not be confused with Mesopotamian Chaldea.
In earlier periods in Urartian and Assyrian sources there is no mention of any Mardes and derived terms. So their arrival might have occured between 600-400bc. Nevertheless there are few indirect evidences pointing to the possibility that it could have occured rather early. First it's the term Mardali (Մարդաղի) in Taron. Mardali is usually linked with Mardes but the presence of -li suffix suggest an interaction with Urartian language speakers where -li is a plural suffix in Urartian. Then there is another term [marda] in Urartian language. This term is mentioned once and it's meaning is obscure. Nevertheless it's known that it relates to some kind profession. Common nouns derived from ethnic names is not rare so it's quite possible that it is derived from Mard tribe. Although it can be a chance coincidence or just a loanword from an IE language.
Anyway Mardes were present in Armenia quite early and it is even possible that some of them were relocated by Urartian rulers from eastern regions. This would fit with their status in Orontid army as mercenaries. But a post-Urartian arrival is also possible. They are mentioned in Tigran's army also. Based on that some suggested two waves of migrations. Terms like Mardastan, and noble family Mardpetuni also derive from this tribal name. Mardin is another possibility although it has other etymologies also.
Their initial homeland was in most likelihood in South Caspian region. Iranian archaeologists suggest a possibility that Iron Age culture Marlik (known also as Talish culture) is related to Mardes. So we can expect to have their DNA. They were neighbors of Medes but not necessarily related to them. They were an Iranian tribe based on their name but the root from which it is derived is unrelated to the name Medes. Moreover Mardes are described as enemies of Zoroastrian religion and given Medes close relationship with Zoroastrian religion further reduce the chance that Mardes and Medes were identic.
So the conflation of Medes and Mardes is very dubious. For instance it's not supported by Vardanyan. See the second picture.
This conflation is used as an argument for a theory that Mardes were Kurds or even proto Kurds. But Armenian sources use only the term Medes for Kurds. Kurds are referred in medieval Armenian sources as "azg marac''" which means Medes nation. Why Armenian historians used Medes ( Մար ) for medieval Kurds is a different subject.
For the etymology of Mardes two theories exists. One is derived from the Persian word martiya meaning man. Notice the Armenian word mard meaning man is also derived from the same PIE root. This etymology would support the idea that Mardes were a Persian tribe claimed by Herodotus. Another etymology is the mareda meaning killer.
One can compare in the link below and see that Persian term is the closest. While the Kurdish form is more distant. The word by the way is present and Turkic and Finno-Ugric languages also.
And finally few names we know from Mardpetuni clan are typically Armenian. Like Arsen and title Hayr. So this mean that during Arshakid period they were fully assimilated and Armenian speakers.