a kidney (plural), i.e. (figuratively) the inmost mind
Usually translated as
reins
Origin
of uncertain affinity
Occurrences
Nephrós occurs 1 time in the King James.
Distribution of the word across the Bible: Revelation (1)
Revelation 2:23 — And I will kill her children with death; and all the churches shall know that I am he which searcheth the reins (νεφροὺς) and hearts: and I will give unto every one of you according to your works.