detto

Detto is the Tuscan Italian past participle of dire (to say), from Latin dictum (something said). The form ditto emerged as a variant. In Italian commercial writing of the seventeenth century, ditto (or detto) was used to avoid repeating a word — particularly in lists, invoices, and accounts. '10 yards of silk... ditto of cotton' meant '10 yards of cotton.' The word replaced the repetition. The replacement was the point.

English adopted ditto in the early seventeenth century for the same purpose: avoiding repetition in commercial documents. The ditto mark (〃 or ″) — two small marks placed below a repeated word — became standard in accounting and list-making. The word and the mark served identical functions: they said 'same as above' without saying 'same as above.'

By the nineteenth century, 'ditto' had moved from bookkeeping to conversation. 'Ditto' as a spoken word meant 'I agree' or 'same here.' The brevity was the appeal — one word replaced a sentence. The 1990 film Ghost cemented the conversational usage when Patrick Swayze's character says 'ditto' instead of 'I love you.' The bookkeeping abbreviation became a romantic catchphrase.

Ditto also became a brand name: the Ditto machine (also called a spirit duplicator) was a common office duplication device from the 1920s through the 1980s. The word for repetition named the machine that made copies. Students of the 1970s remember the smell of ditto sheets — the purple-inked copies distributed in classrooms. The word for 'same as above' became the word for the copies and the word for agreement, all at once.