Gr. phren (1) diaphragm, and (2) brain. From this word, which dates back to the time when the heart was thought to be the seat of emotions, two series of terms have been derived. From its first meaning, heart or diaphragm, we get the name of the phrenic  nerve. On the other hand, from its second meaning for brain, we get phrenology and several compound terms ending in phrenia (such as schizophrenia).