Definition from Wiktionary, the free dictionary
Ancient Greek 
From Proto-Indo-European *per- (“to go over, through, very, exceedingly”).
- (5th BC Attic): IPA: /pró/
- (1st BC Egyptian): IPA: /pro/
- (4th AD Koine): IPA: /pro/
- (10th AD Byzantine): IPA: /pro/
- (15th AD Constantinopolitan): IPA: /pɾo/
- “fore”, that is, in front of, prior (figuratively superior) to.