The story
Originating from a parody sketch titled "Hell's Cafeteria", featured in the 19th episode of the talk show The Late Late Show with James Corden, which first aired on April 27, 2015. In the episode, British celebrity chef Gordon Ramsay holds the head of American television personality Julie Chen between two slices of bread. He then asks her, "What are you?", to which she replies, "An idiot sandwich."
Etymology from Wiktionary, CC BY-SA 4.0.