This could have been described under CBT too. As the word clearly indicates, it handles the balls of men.
The statement; that man has balls, is very true here because if you want to be able to receive my booted feet, with which I first carefully kick you in the nuts, and then gradually increase the pressure, you really should have “balls”.
Will you lose courage and fall crying to the floor pleading for mercy, or will you take heart and hold out waiting for the next kick?