Etymology of the Greek word pneuma (πνεῦμα)
the Greek word pneuma, πνεῦμα (a current of air; breath (blast) or a breeze; by analogy or figuratively, a spirit; (human) the rational soul, vital principle, mental disposition, etc., or (superhuman) an angel, demon, or (divine) God, Christ's spirit, the Holy Spirit)
derived from the Proto-Indo-European root *pneu-
derived from the Greek word pneo, πνέω (to breathe hard; breeze)