Greek "mysia", German Mysien/Moesien, Cyrillic " Mizija"

Hi people,

I have been trying to check the etymology and original reference of
the Greek name "Mysia". At least two geographical regions have been
called with this name in Greek: the "Mysia" (German "Mysien") in the
Middle East and the "Mysia" (German, with obviously Latin origin,
"Moesien"). Both names are transcibed with an "i" in the place of
"y" into Cyrillic, which is the normal case (gr. i, y > cyr. i). I am
not sure the name is used for the region in the Middle East though
(including in my own language, I have to look this up).

My questions are:

1. Is there information on which was the original reference of this
name (the European or the Asiatic "Mysia"?). How did it turn out that
two reagions were called with this name (including some others like a
not so popular "Mysia" in Parthia, etc.)?

2. I can imagine that certain problems with interpreting historical
accounts in the Greek language arise from this double reference. How
are those dealt with?

3. Can a Greek and IE etymology of the word be reconstructed, what
does the name mean?

4. Is there an explanation why the German language adopted the Greek
spelling for the region in the Middle East and the Latin spelling for
the European region under the same name?

5. To speakers of Slavic languages: is the word Mizija (or something
similar) used to describe a region in the Middle East? I am
personally not quite sure about Bulgarian, but I need to look it up or
ask a historian.

I am just trying to collect information on this geographical name
since a discussion arose a few weeks ago in my institute that left
lots of question marks unresolved.

Thank you.

Evelina