νεφρός nephrós

Meaning

a kidney (plural), i.e. (figuratively) the inmost mind

In the King James Version: reins

Derivation: of uncertain affinity;

Where it is used

• Revelation 2:23 Then I will strike her children dead, and all the churches will know that I am the One who searches minds and hearts, and I will repay each of you according to your deeds.