The only free and comprehensive online etymological dictionary of the Spanish language
regir (Verb) "to rule"
14th cent. From Latin regere "to rule," "to lead." From Proto-Italic *reg-e/o- "to direct." From Proto-Indo-European *h3reǵ-e/o- 'id.'
Indo-European
Romance
Portuguese reger, French régir, Italian reggere
Italic
Umbrian rehte "right"
Celtic
Gaulish regu-c "I stand up," Old Irish a-t-raig "to stand up," Middle Welsh reaf 'id.,' Old Breton gurre "to raise," Middle Cornish gorre "to put"
Germanic
Gothic -rakjan "to stretch," Old Norse rekja "to wrap," Old High German recken "to stretch," Old Saxon rekkian "to explain," Old English reccan "to stretch"
Indo-Iranian
Sanskrit raj- "to direct," Old Persian rāsta- "straight," "justice"
Tocharian
B räk- "to extend"