The person that Butch Weldy didn't know at all is the person who caused the workplace accident in which Butch's legs were broken and his eyes "burned crisp as a couple of eggs." The accident left Butch disabled, blind, and without any compensation—his employers were not required to accept any responsibility, on the grounds that, according to the judge, the accident was caused by one of Butch's co-workers.

His repeated refrain of "I didn't know him at all" seems to be an attempt on Butch's part to process what has happened—that his life has been irrevocably changed by this accident. He doesn't know who did this to him, and nobody but him is going to pay for the losses that he has suffered. In other words, while Butch will suffer for the rest of his life, the unknown person responsible for this disaster will never be identified or punished.

Butch Weldy is blinded by a workplace accident. As he testifies in court about the incident, he is most likely seeking compensation from his employer for his injuries. The "him" in the poem is the same person as Butch Weldy's "fellow servant" and the same someone who "left a blow-fire going." In other words, he is the person responsible for Butch's blindness. Because of "him," Butch will be blind without any type of workers' compensation, and at the poem's end, Butch is flabbergasted that someone who is responsible for changing his life so drastically is a person whom he does not even know. He is looking for someone to blame and to hold accountable, but he goes to his death (hence, his epitaph) without even that slight satisfaction.