BT Sot 45b(41) :במאי קמפלגי, מר סבר, עיקר חיותא בטיבוריה, ומר סבר, עיקר חיותא באפיה הוא‏ : what do they disagree about? one master thinks the essence of the life-force is in his navel, the other master thinks the essence of the life-force in his face
See the entire entry for ḥayyū, ḥayyūṯā n.f. life

BT Sot 45b(41) :עיקר חיותא בטיבוריה‏ : the essence of the life force is in his navel
See the entire entry for ṭybwr n.m. umbilical cord