Mutes at funerals, who wore a black cloak; sometimes called the Black Guards.
I do pray ye To give me leave to live a little longer. You stand about me like my Blacks.
Beaumont and Fletcher: Mons. Thomas, iii. 1.
(The ), or “The 7th Dragoon Guards,” or “The Princess Royal's D. G” Called blacks from their facings. Nicknames: “The Virgin Mary's Guard,” “Straw boots,” “Lingoniers,” etc.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894