"You wanna know who Fred Krueger was? He was a filthy child murderer who killed at least 20 kids in the neighborhood... kids we all knew. ... It drove us crazy when we didn't know who it was, but it was even worse after they caught him. (Did they put him away?) Well, all the lawyers got fat and the judge got famous, but someone forgot to sign the search warrant in the right place and Krueger was free just like that. (What did you do?) A bunch of us parents got together and tracked him down. We found him in old abandoned boiler room, where he used to take his kids. ... We took gasoline and poured it all around the place and made a trail of it out the door. We lit the whole thing up and watched it burn. He's dead now. He's dead because Mommy killed him." - Marge Thompson speaking to Nancy Thompson about Freddy Krueger
Frederick Charles "Freddy" Krueger was born in Springfield, Ohio, as The Bastard Son of 100 Maniacs when his mother, Amanda Krueger, was brutally raped and beaten by inmates at The Westin Hills Asylum, a place where she volunteered at as a nun. Two careless guards had accidentally locked her up in the hospital over the holiday weekend. When the guards had returned to go to work as normal, they found Amanda, bruised and beaten. The inmates had left her for dead, but she was still alive and, as a result of the inmates assaulting her, pregnant.
After this, Amanda gave her son, Frederick, up for adoption. Fred was adopted and raised by Edward Underwood, an abusive alcoholic. His classmates at school would ostracize him due to him being "The Son of 100 Maniacs". Between the humiliation from his peers and the physical abuse from his foster father, Fred took out his anger on animals, killing them in brutal ways. Eventually, he switched to cutting himself for pleasure. He killed his foster father with the same shaving razor he used to cut his chest, making him his 1st victim.
Fred grew up and got married to a woman named Loretta and raised a child with her named Katherine. He got a job as a custodian at the Springwood Power Plant. He primarily worked in the boiler room, which he turned into his personal workshop, where he secretly crafted weapons (one of which being his iconic bladed glove). His family and his superiors knew nothing of this "hobby".
Later on, Freddy would become a child murderer nicknamed "The Springwood Slasher". His M.O. was bringing victims to his boiler room and slashing them with a bladed leather glove, which he had made himself. He would then throw the bodies in the furnace to get rid of the evidence. When Loretta found out that he was actually the killer all along, he took her to the basement and slashed her, but what he didn't know was that his daughter, Katherine, was watching the whole thing. Scared of her father, she promised not to tell anyone about what she saw. This wouldn't matter though, as the police would search his lair and find some damning evidence of his crimes.
He was brought to court for his alleged crimes, but due to a technicality (The intoxicated judge hadn't signed the arrest warrant in the right place, and on top of that, the police didn't even read him his Miranda Rights.), he was released. Outraged, the vigilant parents of Elm Street took it upon themselves to track Freddy down in his boiler room and burn him alive. Freddy, however, lived on in a new form, thanks to the evil spirits, known as the dream demons, that had granted him the power to haunt people in their dreams, and affect their real lives through their dreams as well. Freddy could kill a person in their sleep just through killing them in one of their dreams, blurring the line between dream and reality.