The key elements in All Might's back story include his quirkless start which made his journey to becoming a hero more challenging. Then there's the fact that he received One For All, which was a huge turning point. Also, his role as a symbol of peace and his decline in power over time due to the nature of the quirk are important aspects.
All Might, originally Toshinori Yagi, was a quirkless boy with big dreams. Nana Shimura recognized his potential and passed on One For All to him. This quirk was not easy to master. All Might had to endure a great deal of physical pain and strain. He spent years building his reputation as the world's greatest hero. His back story is one of perseverance and self - sacrifice. He knew that his time as All Might was limited due to the toll the quirk took on his body, yet he still carried on, inspiring generations of heroes with his story.
One possible back story is that the maid was a student who had to drop out of school due to financial problems. She then decided to become a maid to earn money and hopefully one day go back to her studies. She may be constantly trying to improve herself in her free time so that she can achieve her educational goals in the future. She might also have dreams of getting a better job after saving enough money from being a maid.
Another possibility is that Miss Rachel has a back story related to her career. She might have had big dreams when she was young but faced numerous obstacles. For example, she could have been discriminated against in her field due to her gender or some other factor. This would have made her work even harder to prove herself, and this aspect of her back story would be important in understanding her motivation and determination in the overall story.
The key elements are being Quirkless at first. Then, the mentorship of Nana Shimura. And of course, receiving the One For All Quirk. These are the main things that shaped his origin.