dittoyoudaoicibaDictYouDict[ditto 词源字典]
ditto: [17] Ditto is a precisely parallel formation to English said ‘aforementioned’ (as in ‘the said John Smith’). It is the Tuscan dialect version of Italian detto, which comes from dictus, the past participle of Latin dīcere ‘say’ (source of English dictionary and a vast range of related words). It was originally used in Italian to avoid repeating the name of the month when giving a series of dates, much as inst and ult are used in commercial English.
=> diction, dictionary[ditto etymology, ditto origin, 英语词源]
dittoyoudaoicibaDictYouDict
1620s, Tuscan dialectal ditto "(in) the said (month or year)," literary Italian detto, past participle of dire "to say," from Latin dicere (see diction).

Originally used in Italian to avoid repetition of month names in a series of dates; generalized meaning of "same as above" first recorded in English 1670s. Dittohead, self-description of followers of U.S. radio personality Rush Limbaugh, attested by 1995. dittoship is from 1869.