black slavery started around the 15th century, and it was not long the negative words included "black" in them. here's a snippet of history of phrases that came about after slavery started. It wasn’t until the late 1580s that “black” was used figuratively to mean “having dark or deadly purposes, malignant; pertaining to or involving death, deadly; baneful, disastrous, sinister,” according to the OED.
The published usages include “black curse” (1583); “black name” and “black Prince” (1599, Shakespeare); “blacke edict” and “blacke victory” (1640); “black moment” (1713); “black enemy” (1758); and “black augury” (1821, Byron).
Around the same time, “black” took on other negative meanings, including horribly wicked or atrocious, as in “blacke soule” (1581); “blacke works” (1592); “blackest criminals” (1692); “blackest Calumnies” (1713); “black ingratitude” (1738, Macaulay); “the blackest dye” (1749, Fielding); and “black lie” (1839).
In the 17th and early 18th centuries, “black” also became identified with sorrow, melancholy, gloom, and dire predictions; a “black” outlook was pessimistic, whereas “bright” meant hopeful.
The word “blackguard” originally referred to dirtiness rather than to evildoing. It originated about 1535, and according to the OED it was first used first to refer to a scullery or kitchen worker, someone who had charge of pots and pans.
“Blackguard” was later used to describe a street urchin who worked as a shoe-black. In 1725, Jonathan Swift wrote of “The little black-guard / Who gets very hard / His halfpence for cleaning your shoes.”
And a 1785 slang dictionary described a “black guard” as “a shabby dirty fellow; a term said to be derived from a number of dirty tattered and roguish boys, who attended at the horse guards … to black the boots and shoes of the soldiers, or to do any other dirty offices.”
Boys who picked up odd jobs in the streets were also called “blackguards,” and in 1736 the term was first used to mean a scoundrel.
“Blackmail,” first recorded in 1552, originally meant protection money.
