"Germane" stems from the French "germain" and "German" stems from the Latin "Germani". Don't know if germain and Germani are connected.
Discussion
you just said they were!
The Germani is the name of a tribe, apparently. It comes from a different language and was integrated by Julius Caesar.
well, there you go
did you know there was a tribe of germans on the east of what is the modern borders called "sorb" and the history of this is very obscured but supposedly someone of this tribe got a grant of property in what is now modern former yugoslavia
i forget what other interesting things there were related to this but having spent a lot of time in serbia i can confirm that serbians are very german, except with bad tempers