The first part of The Hail Mary is “Hail Mary, full of grace, the Lord is with you. Blessed are you among women, and blessed is the fruit of your womb, Jesus.” That passage comes to us straight from God through the Angel Gabriel and the Holy Spirit:

Luke 1:26: “In the sixth month, the angel Gabriel was sent by God to a town in Galilee called Nazareth, to a virgin betrothed to a man named Joseph, of the House of David; and the virgin’s name was Mary.”

Luke 1:28 reports that Gabriel announced: “Hail Mary, full of grace. The Lord is with you.”
The second part of the Hail Mary is “Holy Mary, Mother of God, pray for us sinners, now and at the hour of our death, amen.”

Mary went to visit her kinswoman, Elizabeth. (Luke: 1:42) “Now, as soon as Elizabeth heard Mary’s greeting, the child leapt in her womb and Elizabeth was filled with the Holy Spirit. She (Elizabeth) gave a loud cry and said, “Of all women, you are the most blessed, and blessed is the fruit of your womb.”

The last part of the Hail Mary, “pray for us sinners, now and at the hour of our death” comes from the realization that God loved His Mother, and that His Mother, who was in Heaven, could intercede with Him to give us aid and comfort. Mary is not God, and is not worshipped as such, but all good sons listen to their mother.

Many people compare Mary’s position is Heaven to one of us going before a judge in court. If you can get the Judge’s mother to put in a good word for you before the trial, mercy is more likely.

Few among us do not need as much mercy as we can get.

The English historian, William of Malmesbury, said that Lady Godiva (around 1051) had a Rosary made of "precious stones on a wire". 

Over time, the Rosary evolved, most notably with St. Dominic in the 1200s, as a string of beads that allowed people to say 150 Hail Mary’s that duplicated the 150 Psalms, recited by many monks and nuns in the monastic Office. To keep track, beads were strung on a string.
The ten Hail Mary’s in each decade of the Rosary also made it easy to count on the fingers of both hands.

In England, an early word for prayer was “bede”, which is why The Rosary is sometimes referred to as “saying the beads (bedes).

St. Bede, the early English historian, had a Benedictine monastery and school named for him in Peru, Illinois. The inventor of The New Rosary had the great good fortune to have attended St. Bede’s school, and refers to the springy counting bead on The New Rosary as “St. Bede’s bead.”