"And when he had said this, he breathed on them, and saith unto them, Receive ye the Holy Ghost:" - John 20:22 KJV

In the Old Testament, the word for “breath” – “ruwach” - is the same word for “Spirit,” as well and “wind.”

In the New Testament, the word for “breath” – “pnoē” – is (again) the same word for “wind” (also “bloweth.”) The word for “Spirit” (also “Ghost”) is “pneuma.” The root word of “pneuma” is “pneō,” which is above, the word for “breath” and “wind.”

So, we can see that the words “breath,” “wind,” “bloweth,” and “Spirit,” are tied in together.

Jesus compared being born of the Spirit to the wind. (They are the same Greek word.)

"The wind bloweth where it listeth, and thou hearest the sound thereof, but canst not tell whence it cometh, and whither it goeth: so is every one that is born of the Spirit." - John 3:8 KJV

When Jesus was giving His disciples the ‘Great Commission’ in the book of John, the Bible says,

"And when he had said this, he breathed on them, and saith unto them, Receive ye the Holy Ghost:" - John 20:22 KJV

Interestingly, the root word of “breathed” is to “spring up,” “to beget,” “to be born.”

Larry Pierce, in his ‘Outline of Biblical Usage’ makes the comment, “The Greek word here used is employed nowhere else in the New Testament, but is the very one used by the Septuagint translators of Gen 2:7: 'And the Lord God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul.' There, man's original creation was completed by this act of God; who, then, can fail to see that here in John 20, on the day of the Saviour's resurrection, the new creation had begun, begun by the Head of the new creation, the last Adam acting as 'a quickening spirit' (1Cr 15:45)!" (Arthur W. Pink, Exposition of the Gospel of John, p. 1100).”

Thus, just as Adam was ‘born’ when Jesus breathed into his nostrils the breath of life and he became a living soul, Jesus signaled the new birth of His disciples when He breathed on them and said, Receive ye the Holy Ghost.  

On the Day of Pentecost, the sound that was heard is described as a rushing mighty “wind” (“pnoe”), which is the word for “breath” and “wind.” Those in the upper room were receiving the breath of life - the breath of Jesus Christ - the Holy Ghost.