The antecedents of the blackface minstrels were English performers of the late 18th century. The composer and actor Charles Dibden performed the character Mungo in "The Padlock," presented at Drury Lane in 1768. Mungo was the slave of a West Indies planter. Dibden, in blackface, sang this song (part):

Dear heart, what a terrible life I am led!
A dog has a better, that's sheltered and fed.
Night and day, 'tis the same;
My pain is deir game:
Me wish th de Lord me was dead!
Poor black must run,
Mungo here, Mungo dere,
Mungo everywhere:
Above and below,
Sirrah, come; sirrah, go;
Do so, and do so.
Oh! Oh!
Me wish to de Lord me was dead.

Mungo gets drunk in the second act and is profane throughout.
The role was taken up in America by Lewis Hallam, the younger, who first played the part in 1769, in New York. Hallam had studied the talk and actions of black slaves, and his projection of the part was quite different from that of Dibdin. A pantomine, "Robinson Crusoe," pesented at Drury Lane and the Theatre Royal, 1781, with Friday in blackface along with its Savages, was next, and also was performed in New York.

"The Negro On the Stage," Laurence Hutton, Harper's New Monthly Magazine, June, 1889, vol. 79, issue 469, pp. 131-145.
Cornell's The Making of America: Harpers