Daredevil had existed for 20 years before the Teenage Mutant Ninja Turtles showed up in the '80s and yet their origins establish that they are both the products of the same traffic accident and the same mysterious goo.
Daredevil's origin, as shown in Daredevil #1, is that when he was young he saved a blind man from getting hit by a truck, only to have a radioactive canister fall off the same truck and hit him in the face. Between the radioactivity of the substance and the impact of the hit, Daredevil was left blind.
Fast forward 20 years: The creators of the Ninja Turtles were big fans of Daredevil, especially the issues by Frank Miller. Not content with simply borrowing Daredevil's origin, they actually went ahead and wrote their characters into it. In Teenage Mutant Ninja Turtles #1, we see the exact same scene as before only from a different perspective.
After the canister hits the child, it then falls into a sewer and mutates some baby turtles which of course turned them into the loving Teenage Mutant Ninja Turtles that we have come to known.
Via Tinseltown Gazette