The Persian nation contains a number of tribes as listed here. ... : the Pasargadae, Maraphii, and Maspii, upon which all the other tribes are dependent. Of these, the Pasargadae are the most distinguished; they contain the clan of the Achaemenids from which spring the Perseid kings. Other tribes are the Panthialaei, Derusiaei, Germanii, all of which are attached to the soil, the remainder -the Dai, Mardi, Dropici, Sagarti, being nomadic.
—Herodotus, Histories 1.101 & 125
Naturally the name is interesting. Is there any link with modern Germans? Or is the link etymological? Or is it a simple coincidence?
Coincidence. Many of the names in Hdt. 1.125 can't be identified, and the ones that are identifiable are from various widely-separated parts of the Persian Empire; but Herodotos' Germanioi refers to the inhabitants of [Karmania or Carmania](http://en.wikipedia.org/wiki/Carmania_(satrapy)), a region in present-day Iran east of modern Shiraz and north of the strait of Hormuz. This was the name of an Achaemenid satrapy. The root still survives in the name of the modern city Kerman.
See further: D. Asheri, commentary on Hdt. book 1 in A Commentary on Herodotus Books I-IV (Oxford, 2007) at p. 164; New Pauly s.v. "Carmania".
Sorry to be dull!