The phrase “to call a spade a spade” originated in ancient Greece, with Plutarch. Its first use in English was in 1542, in a translation of Erasmus, who was Dutch. The word “spade” in the phrase is used as the earth moving tool, and is the same in several languages. The phrase means blunt talk, and has for hundreds of years. It appeared in an American dictionary as early as 1913.
The term “spade” as an ethnic slur was first recorded in 1928. People often avoid Plutarch’s idiom in modern times so as not to be misunderstood. People who don’t know any better think “call a spade a spade” is racist. It is not.
I know this because I once called out a professor for being racist for using it when I was young and stupid. Boy, did I learn a lesson that day. Tuition well spent.