The secret to befriend a legionnaire is to do baaa (sheep sound) behind their back.
So what I came up: it's either because it's their mascot or about le légionnaire Xarro, blackest of black sheep.
Something of an long standing reputation. It's because when legionnaires are on a mission in the desert, there aren't any women around. But there are sheeps...
Risky joke ;)
One was about as wide-shouldered as high, with huge musculous, brown arms covered with burn scars. He told me his personal speciality was shooting a big machine gun, without tripod, running around Rambo-style, and the burns were from the hot barrel.
Another one proudly displayed his scarred belly: "this is when this guy attacked me with his knife, etc, finally I broke his neck" "this is when in Chad I received a 7.62 bullet" "this is when I was drunk and had a fight in Libreville".
Funny guys, better have them as friends than enemies :)