Don't assume blacksmith = devil = evil. Wayland the Smith was the prototype ancient smith god and not evil.

I just ran a search for "black" and "devil" in the same song in the DT and came up with 50 hits. A few tidbits from these:
   My wife she's the devil, she's black as the coal (Fathom the Bowl)
   similar: My wife, she's the devil, she's black (Dick Darby)

See: Black Fox
    Wedding at Stanton Drew