Trivia: Across the hall from Nelson and Murdock is an office that reads "Atlas Investments", a nod to the comic company (Atlas Comics) that would later become Marvel. The logo is the same as that of Atlas Comics too.
Trivia: Wilson Fisk's code-name of Kingpin isn't acquired until season 2. However, his eventual nom de guerre is foreshadowed in season 1 by the way of Ben Urich's cork-board in his office, which features a king of diamonds playing card pinned to it.
Chosen answer: After some research, I can say that no, Cass is not a character of Marvel, nor is he present in the Netflix show. As far as I can tell, it's either a real person, or a random name chosen for the coffin, most likely the former. In another season of Daredevil, the show utilized a real cemetery displaying real names in the tombstones.