Probably from an obsolete phrao (to rein in or curb; compare phrasso); the midrif (as a partition of the body), i.e. (figuratively and by implication, of sympathy) the feelings (or sensitive nature; by extension (also in the plural) the mind or cognitive faculties) -- understanding.
see GREEK phrasso
1. the midriff or diaphragm, the parts about the heart.
2. the mind; the faculty of perceiving and judging: also in the plural; as, 1 Corinthians 14:20.