I have recently read the english translation of Witold Pilecki report into the time he spent in Auschwitz Available here. In it he refers to those who have basically given up the will to live as 'Muslims' I was wondering what the origin of this phrase was. Is it a colloquial term a mistranslation or something else.
If you search for ["Muslims"] in the document linked you will find a paragraph on it
It was a "slang" word (German Muselmann, Polish muzułman - note that the proper Polish for muslim is "muzułmanin") used among inmates and as far I know the origins of the term aren't completely clear.
It was concentration camp slang that referred to prisoners who had been mentally broken, who consigned themselves to death and just stopped caring about trying to survive. Tadeusz Borowski's semi-fictional autobiography of life in Auschwitz (This Way for the Gas, Ladies and Gentlemen) defines the term thusly:
'Muslim' was the camp name for a prisoner who had been destroyed mentally and physically, and who had neither the strength nor the will to go on living - a man ripe for the gas chamber.