E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.
Black Letter Day.
An unlucky day; one to be recalled with regret. The Romans marked their unlucky days with a piece of black charcoal, and their lucky ones with white chalk.
1
Black-letter dogs. Literary antiquaries who poke and pry into every hole and corner to find out black-letter copies of books.
