One interesting thing that J.E. Lighter, A Historical Dictionary of American Slang, volume 2 (1997) makes clear is that at least one and possibly two terms that use the wording "idiot X" arose as TV slang before "idiot box." Here is Lighter's entry for "idiot board": idiot board n. IDIOT CARD 1 ["TV. a cue card"]; hence, the pane of a TelePrompTer.
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