Meaning

noun a mark used to indicate the word above it should be repeated

verb repeat an action or statement

originFirst attested in 1625. From regional Italian ditto, variant of detto, past participle of dire (“to say”), from Latin dīcō (“to say, to speak”). Not related to English dittography. The specific meaning of making copies of paper comes from ditto machine, a genericization from the brand name of a spirit duplicator.

Etymology from Wiktionary, CC BY-SA 3.0