It's usually a feature of the Manic Pixie Dream Girl, but sometimes your Action Gal explains her usually manly feats with "I have brothers". The brothers are almost always older, and numerous, and our female lead has learned to hold her own against them as some form of survival skill.
Sometimes, there are no brothers, the mother is usually out of the picture1, and the father "didn't know how to raise a girl" so did all the boy stuff with her.
There's only one film I can think of where this trope is slightly subverted and the female mechanic of the team explains that her father, "wanted two boys, one to carry on his work as a mechanic and the other to become a heavyweight boxing champion. But he got us..." That film is the obscure Disney classic, Atlantis.
Though it is the only instance where a father teaches girls "boy things" anyway, it's still a skill set that the girl learns through someone else's intervention. She has no self-agency to learn these things herself.
Not once has a woman on screen ever said, "Well, I have a shit car and it's all I can afford on womens wages, and I got tired of calling the local shyster mechanic, so I went and took some courses."
Or: "It's a basic survival skill, why are you so shocked?"
Or: "You don't?" without any further explanation.
It's like the media can't conceive of any woman existing after 1970-something, when having brothers was an acceptable method of learning manly feats. As far as the media is concerned, fictional ladies haven't got much further than Women's Lib.
Next Trope on the chopping block: Supergendered Fat which is a variant of the trope page and I will go into this in more depth. Later.
Most of the time, she's dead. ↩