Hudibras, Part III. Canto 1. line 1385, &c.
It will be seen that Butler, like Fuller, uses the term in the simple sense as a guard of the Prince of Darkness. But the concluding lines of Hudibras's address to Ralpho explain the process by which, at a late period, this term of the Black Guard came to be applied to the lowest class of domestics in great establishments.
The Black Guard of Satan was supposed to perform the domestic drudgery of the kitchen and servants' hall, in the infernal household. The extract from Hobbes (Vol. ii., p. 134.) refers to this:—
"Since my Lady's decay, I am degraded from a cook; and I fear the Devil himself will entertain me but for one of his black guard, and he shall be sure to have his roast burnt."
Hence came the popular superstition that these goblin scullions, on their visits to the upper world, confined themselves to the servants' apartments of the houses which they favoured with their presence, and which at night they swept and garnished; pinching those of the maids in their sleep who, by their laziness, had imposed such toil on their elfin assistants; but slipping money into the shoes of the more tidy and industrious servants, whose attention to their own duties before going to rest had spared the goblins the task of performing their share of the drudgery. Hudibras apostrophises the ghost as—
"... some paltry blackguard sprite
Condemn'd to drudgery in the night;
Thou hast no work to do in th' house
Nor half-penny to drop in shoes;"
and therefore, as the knight concluded—"this devil full of malice" had found sufficient leisure to taunt and rally him in the dark upon his recent disasters.