The word "breathed" in Greek is emfusao, which means "to blow or breathe upon." It is used only here in the New Testament and, according to "The NAS New Testament Greek Lexicon," is used only once in the Septuagint (Greek translation of the Old Testament used in Jesus' day) and that in Genesis 2:7 where God "breathed into [Adam's] nostrils the breath of life."
God emfusao into Adam's nostrils the breath of life.Jesus emfusao on his disciples and said, "Receive the Holy Spirit."
John would have known the use of emfusao to describe that first breath from God into man and intentionally chose it instead of a more common word to describe what Jesus did in that locked room. Why? Did the disciples feel something new and different happening to them? Did it feel like they had suddenly been filled with life?
"Spirit" in Greek is pneuma, which has several meanings and is used 380 times in the New Testament. It is the word used for the Spirit--he who is God--but note that the word "holy," hagios is used to describe the kind of pneuma: that which is most holy (which is a whole other study for this word hagios is also used to mean "saints," something we, as believers, are said to be). Pneuma is also the word for that spirit in us that is life ("i.e. the vital principal by which the body is animated."), for angels and demons and for wind and the movement of air including the act of breathing.
Jesus breathed breath, life, spirit into his disciples but not just any breath, life or spirit, but that most holy of spirits, God. In essence, he, being God, breathed part of himself, God, into them.
Augustine in On the Trinity and in reference to this passage writes:
For that bodily breathing, proceeding from the body with the feeling of bodily touching, was not the substance of the Holy Spirit, but a declaration by a fitting sign, that the Holy Spirit proceeds not only from the Father, but also from the Son. For the veriest of madmen would not say, that it was one Spirit which He gave when he breathed on them, and another which He sent after his ascension (Acts ii.1-4). For the Spirit of God is one, the Spirit of the Father and of the Son, the Holy Spirit, who worketh all in all.I have no problem with the second half of this quote but I wonder: Was Jesus' breathing on his disciples just a sign or promise of what was to come at Pentecost as Augustine suggests (and with whom most commentators agree) or did something substantial occur? If so, why did John compare it to God's first breath into Adam? And if something substantial did occur, what was it and how did it differ from the outpouring of the Spirit at Pentecost? Any thoughts?