Persons exactly like each other, as the brothers Dromio. So called from the Menæchmi of Plautus.
In the Comedy of Errors, not only the two Dromois are exactly like each others, but also Antipholus of Ephesus is the facsimile of his brother. Antipholus of Syracuse.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894