Stories We Like: A Guide to the Comma
"The invitations to the musicale came sliding in by pairs and threes and spade flushes." [O.Henry, "Cabbages & Kings," 1904]Derogatory meaning "black person" is 1928, from the color of the playing card symbol.
To speak directly and bluntly; to avoid euphemism: “The prosecutor said, ‘Let's call a spade a spade. You didn't borrow the money, you stole it.’”
A black person: The spades inhabited Harlem and let the ofays have Wall Street to themselves
[1928+; fr the color of the playing-card symbol and fr the phrase black as the ace of spades]