It’s a crucial line in the 1990 movie Ghost, a favorite phrase of Rush Limbaugh’s dittoheads, and the reigning copy machine of the mid-20th century, but what does ditto really mean, and where did it come from?
“Ditto” as a response meant as “same here” or “what you said” has a modern, almost slangy feel to it, so many people assume that it was taken from the copy machine use. The reading is that a ditto machine makes copies, so saying ditto creates a “copy” of something that was just said. But the “what you said” use is centuries older than the machine.
It comes from Italian ditto, a dialect variation on detto, meaning “said," the past participle of dice, “to say.” It was used in Italian as in il ditto libro, “the aforesaid book.” In English, it came to be used in the 17th century to avoid having to repeat words and phrases in accounting and commercial language. Instead of repeating something like January 29 or Newcastle upon Tyne in a list, one could just put ditto in after the first occurrence.
Ditto gradually drifted from a noun meaning “the aforesaid” or “the same” (as in a 1759 cookbook: “Parsley roots, and leaves of ditto”) to an adverb meaning “I agree with what you just said.”
The force of ditto goes beyond mere agreement though. If the Patrick Swayze character in Ghost said “I love you” and Demi Moore said “Agreed” or “I concur,” it would sound like she was agreeing only with the proposition he expressed: that he loved her. Kind of rude. What she means is not just “I agree,” but “I hereby say the same.” Ditto still carries the concept of actual saying with it. It performs an act of saying by merely pointing back to already said words.
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