An Etymological Dictionary of the German Language/Vernunft

by Friedrich Kluge

Vernunft, f., ‘reason, understanding,’ from MidHG. vernunft, OHG. firnunft, f., ‘activity of perception, sensual perception, comprehension, insight, understanding’; abstract of vernehmen, ‘to hear, perceive, understand,’ MidHG. vernëmen, OHG. firnëman, ‘to perceive, hear, experience, grasp, seize, understand.’ These figurative meanings are based on some such meaning as in Goth. franiman, ‘to take possession of, seize.’ For a similar evolution see vergessen (with different senses attached to the prefix); begreifen has been similarly developed in its figurative senses.