The Ones We Leave Behind - S1-E12
Revealing mistake: When Matt is running across the rooftops doing Parkour to keep up with the car he's following, there is a shot of him running towards another roof about to jump. In this shot, it's clear there is a stunt double in Charlie Cox's place. (00:29:27)
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.