Why did Jesus give Simon the name, "Rock"?

Perhaps you never wondered. Here’s why. Because He wanted all to know that Simon would be he to whom all must turn who want to know God’s will. There is a precedent for this in Scripture:

Exodus 7:1
King James Version (KJV)
7 And the Lord said unto Moses, See, I have made thee a god to Pharaoh: and Aaron thy brother shall be thy prophet.

Exodus 18:13-15
King James Version (KJV)
13 And it came to pass on the morrow, that Moses sat to judge the people: and the people stood by Moses from the morning unto the evening.14 And when Moses’ father in law saw all that he did to the people, he said, What is this thing that thou doest to the people? why sittest thou thyself alone, and all the people stand by thee from morning unto even?15 And Moses said unto his father in law,
Because the people come unto me to enquire of God:

Exodus 19:9
King James Version (KJV)
9 And the Lord said unto Moses, Lo, I come unto thee in a thick cloud, that the people may hear when I speak with thee, and believe thee for ever. And Moses told the words of the people unto the Lord.

God put Moses in a position of authority over the people. Jesus has done the same thing with Simon. God covered Moses with the Cloud, Jesus gave Simon His own name, Rock, along with the keys to the Kingdom (Matt 16:18-19) and appointed him Shepherd over the Church (John 21:15-17).

In the same way, Jesus has appointed Simon as Shepherd over His flock.

John 21:15-17
King James Version (KJV)
15 So when they had dined, Jesus saith to Simon Peter, Simon, son of Jonas, lovest thou me more than these? He saith unto him, Yea, Lord; thou knowest that I love thee. He saith unto him, Feed my lambs.

16 He saith to him again the second time, Simon, son of Jonas, lovest thou me? He saith unto him, Yea, Lord; thou knowest that I love thee. He saith unto him, Feed my sheep.

17 He saith unto him the third time, Simon, son of Jonas, lovest thou me? Peter was grieved because he said unto him the third time, Lovest thou me? And he said unto him, Lord, thou knowest all things; thou knowest that I love thee. Jesus saith unto him, Feed my sheep.

And in order to bring this point home, Jesus gave Simon His own name, “Rock” or “Peter”.
This is to signify the type of authority which Jesus has given to Simon. He has the authority to bind and loose in the God’s name.

Matthew 16:18-19

Ok, let's go through it.

18 And I say also unto thee, That thou art Peter,

Jesus, speaking to Simon, names him "Rock". That is the meaning of the name "Peter". Heretofore, the only Rock in Scripture has been God. Therefore, Jesus has given Simon, His own name. This is significant. It means that Simon is now God's representative upon earth. The rest follows logically.

and upon this rock I will build my church;

Since Peter is Christ's representative, it is logical that Jesus would organize His Church around St. Peter. This is why we can say that the Church is the Body of Christ. It is Christ's CORPORATION. St. Peter is the Chief Officer. The Apostles the Board of Directors.

and the gates of hell shall not prevail against it.

Again, because Peter is Christ's representative, it is logical that the Church will prevail against the gates of hell. Hell is in a state of siege from the moment that Jesus was conceived. Upon His death, Jesus stormed hell and set the captives free:

Hebrews 9:15-17
15 And for this cause he is the mediator of the new testament, that by means of death, for the redemption of the transgressions that were under the first testament, they which are called might receive the promise of eternal inheritance.
16 For where a testament is, there must also of necessity be the death of the testator.
17 For a testament is of force after men are dead: otherwise it is of no strength at all while the testator liveth.

From this point on, the Catholic Church, which Jesus established, has kept Satan in a state of siege. From the moment that any man is baptized, they are snatched out of Satan's hands and joined to the Church:

Acts 2:38Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.….47 Praising God, and having favour with all the people. And the Lord added to the church daily such as should be saved.

The Catholic Church sets the captives free in the name of Jesus Christ. Therefore, the gates of hell do not prevail against that infallible institution which Jesus Christ built upon that infallible office.

19 And I will give unto thee the keys of the kingdom of heaven: and whatsoever thou shalt bind on earth shall be bound in heaven: and whatsoever thou shalt loose on earth shall be loosed in heaven.

Everything which Peter binds upon earth is bound in heaven. Everything he looses upon earth is loosed in heaven. That is not only infallibility. That is also saving power. God has given the office of Peter awesome power. And all that we can do is sit back and gasp:

Matthew 9:8
8 But when the multitudes saw it, they marvelled, and glorified God, which had given such power unto men.

Yeah! Christ willed the Pope's teachings Ex cathedra, infallible!