Does anyone have information regarding when And exactly how that idiom initial came into use? Specifically, I'm puzzled about the use of the term "free" in conjunction with "white", simply because no white folks were slaves in the U.S.美国担心中国月球探测器「玉兔」轧了阿姆斯特朗的脚印，会出现这种情况吗？如何保�