Joss Whedon might not know who his cinematic Batgirl is going to be just yet, but he does know what story he wants to tell. "I started getting obsessed with how a young woman could get hardcore enough to need to put on the cowl. Like, what's her damage?" he told Heat Vision Wednesday. "Who is this person, who decides - rather than being forced to by their childhood trauma - decides to pick up this life?"
In DC's comic book mythology, there have been all manner of women who've worn the cowl. Here's what their damage is.
Batwoman 1 (Kathy Kane; 1956)
Kathy Kane has the simplest of origins: a former circus performer, she was a fan of Batman - "the greatest acrobat of all!" as she called him - who was jealous of his ability to use his skills to fight crime. When she inherited a fortune from her uncle, she was able to quit her career and devote herself to becoming a bat of her very own. In her defense, it was the 1950s, when crime fighting seemed like a fun pastime for those with athletic skills and a good heart.
Bat-Girl 1 (Betty Kane; 1961)
If Kathy Kane's origins seem naive from today's point of view, her sidekicks verge on the ridiculous; upon sharing a hairbrush with her aunt Kathy, she realizes that she's the niece of Batwoman - which makes her create her own superhero costume and decide to get in on the family business. Unlike Batwoman, she's got no athletic training, but she is good at tennis.
Batgirl 2 (Barbara Gordon; 1967)
What caused Barbara Gordon become Batgirl? An accident, basically; she created a Batgirl costume for a party, only to end up having to save the day for real while wearing it. That gave her a taste for do-gooding, which led her to train hard ("I'm stronger and harder than I've ever been, thanks to my special protein diet and intensive exercise!" she thinks to herself in Detective Comics No. 359, the 1967 story that told her origin) and take up superheroing for real.
Batgirl 3 (Helena Bertinelli; 1999)
Bertinelli is the first Batgirl/Batwoman to have genuine trauma in her past: the daughter of a mob boss, she watched her entire family be murdered by a rival crime family when she was a child. That led her to become the vigilante known as the Huntress, and later - when Batman temporarily disappeared and she felt Gotham needed a hero - a short-lived Batgirl.
Batgirl 4 (Cassandra Cain; 1999)
Another product of childhood dysfunction, Cain was raised by one of the world's greatest assassins to follow in the family business, with an upbringing that taught her to read body language as a preemptive defensive/analytical move as opposed to being socialized. Her becoming Batgirl was part of a wider attempt to save her from the future her father had envisioned for her.
Batwoman 2 (Kate Kane; 2006)
The rebooted Batwoman has it all - a socialite who lost her sister and mother as part of terrorist attack as a child, and put that trauma into being a soldier until her admission of being a lesbian saw her dismissed. After fighting off a mugger in Gotham City, she decides to use her anger and experience to become a crime fighter in her own right. Like the Bertinelli Batgirl, she also made her cowled debut during a point where Batman was out of town.
Batgirl 5 (Stephanie Brown; 2010)
Brown wasn't driven by childhood trauma per se, but she was in the superheroing game before taking up the cowl because of her upbringing - or, more specifically, the discovery that her father was a supervillain and her role in preventing his plans coming to fruition. She had a career as the crime fighter Spoiler for some time before becoming Batgirl, eventually taking on the role at the urging of Cassandra Cain (and, to a lesser extent, Barbara Gordon).