The Proto-Indo-European word *er-, ere-, erei-
Word *er-, ere-, erei-
Meaning to move stir, animate, fight, struggle, rise up, to spring up, be born
See also Phrygian: ΕΙΡΟΙ ‘untimely or children’
Synonyms *bʰeudʰ-, *bʰeuh₂- (bʰeuh₂mi [1ps]), *katu-, *weik-, *yeudh-, *nant-

Other words that might be of interest
*k̂at- ‘battle’