Trivia: When Daredevil and Frank are talking in the cemetery, some people thought Charlie Cox was crying when Frank was telling the story about his children. It turns out that Cox was just sweating profusely under his mask from multiple takes of carrying Jon Bernthal up the hill, with some of the sweat trickling down near his eyes.
A Cold Day in Hell's Kitchen - S2-E13
Trivia: In Karen's office there are some frames on the wall, one of them has the title The Battle of New York, referring to the Avengers fighting Loki and the Chitauri army.
Trivia: The Dogs of Hell motor bike gang can also be seen in Agents of Shield.
Trivia: The dogs of hell gang also appeared in the Agents of SHIELD TV show.
Trivia: Daredevil is chained by Frank Castle in a similar way from The Punisher: welcome back Frank #3.
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.