This is my name. I'm a girl and I'm still really confused about my name - it's not common at all, so I can't find much info about it on the net. I heard it was a masculine name but some Arabic lady told me it was Arabic for 'faith' and definitely is a girl's name. For a while, I also read that it meant 'Fearless'. My parents aren't helpful either. So if anyone knows anything about 'Aiman', please comment!
Since a great many people in Kazakhstan are Muslim, Aiman could be connected to the (usually feminine) Arabic name Iman, which means "faith" as the above user was told.