I think steelman is derived as the opposite of strawman. Taken literally, something made from straw is weak, and something made from steel is strong. A strawma

I think steelman is derived as the opposite of strawman. Taken literally, something made from straw is weak, and something made from steel is strong. A strawman is an imaginary opponent who is easy to defeat. Like a scarecrow (a human-like figure stuffed with straw, meant to scare off birds from crops) which would be easy to defeat because it doesn't fight back when attacked.