Started by Edward Smith Stanley, the twelfth Earl of Derby, in
1780, the year after his establishment of the Oaks stakes (q.v.).
The Derby Day
is the day when the Derby stakes are run for; it is the second
Wednesday of the great Epsom Spring Meeting, in May.
The Derby Day.
The Derby, the Oaks, and the St. Leger are called “The Classic
Races.” The Oaks is the classic race for fillies only, three years' old
(£1,000); the Derby (Darby) for colts and fillies three years' old; the
St. Leger for colts and fillies, those which have run in the Oaks or
Derby being eligible.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894