It comes from the words femme fatal and vagina.
1. A bitch
is so dry and tight, you swear it could rip your dick
2. A deadly vagina.
3. A vagina that should be either condemned or feature a warning sign.
4. Any vagina that is hazardous to your sexual health.
I really need to raise my standards. Last night I was fucking
, and she had a total femme vagal. I'm lucky my dick is in one piece.