Comment by chaps

> as far as I can tell they are used interchangeably.

They are not.

> Any chance the distinction existed long time ago"

What is "long time ago"? This stuff isn't exactly gone.

You really need to realize that American slavery really wasn't that long ago. It was only 1975 when the last survivor of American slavery died. Generational effects last and the reverberations of years of oppression still reverb very, very loudly today.