The author, identified in the tradition as Luke the Physician, appears to have been a gentile convert to Judaism who then became a Christian. Luke clearly had the gospel of Mark in front of him as he wrote. He also seems to have had a second source, which some call Q (for Quelle, which means "source" in German). Other scholars, though a minority, suggest that instead Luke had Matthew as his second source. At least we know that Luke employed the Virgin Birth tradition, which Matthew had introduced. (Never, however, does Luke quote the text from Isaiah on which Matthew built his virgin story. Perhaps the problems to which I have previously referred (see Part One of this series of articles) were already known to him). But Luke does develop the story in his own unique way.
Luke opens his story not with the birth of Jesus but with the birth of John the Baptist. He clearly knows the tradition that the Baptist's role was that of preparing the way for Jesus. As a fact of history, it seems obvious that Jesus began his public career as a member of the John the Baptist movement. The scriptures are clear that Jesus was not only baptized by John but also that he did not emerge as a leader in his own right until John the Baptist had been arrested and perhaps even executed.
There are bits of biblical evidence that some competition existed between the followers of Jesus and the followers of John in the earliest years of the Christian movement. By the time the gospels were written (70-100 C.E.), John had been incorporated into the Christian story but in the secondary role of the forerunner, the one "who prepared the way for the Lord." John was even said to have validated Jesus' claim to superiority in his reticence to baptize Jesus, suggesting that he, John, had a need to be baptized by Jesus. So Luke began his gospel by telling a story that suggested that even in the births of these two figures, the pre-eminence of Jesus had been established.
He therefore chose names for John's parents that added greatly to the significance of the story he was determined to tell. He also created the character of John the Baptist by lifting content directly out of the Hebrew scriptures. For Luke, John's identity was best seen not as the new Elijah, but as the nameless voice from the book of Malachi whose task it was to prepare the way for the coming of "the day of the Lord."
In a part of the Hebrew Scriptures called "The Book of the Twelve," Malachi was listed as the last of the Jewish prophets. Malachi's immediate predecessor in those Jewish Scriptures was Zechariah. So Luke used Zechariah as the name of John's father, the Baptist's immediate predecessor. (That choice required an explanation, which Luke added to his story, of why the name John was chosen when none of Zechariah's kinsmen bore that name.)
The choice of the name Zechariah also helped Luke to assert how deeply the book of Zechariah had shaped the early Christian message. Zechariah 9:9-11 gives the embryonic story of the Palm Sunday procession, and elsewhere the book contains a story about the shepherd king of Israel, who was betrayed for 30 pieces of silver by those who bought and sold animals in the Temple. All of these themes show up in the Jesus story. In Zechariah is also found the familiar verse, used by Jesus in almost all the gospels, about the shepherd being struck and the sheep being scattered. So the choice of the name of Zechariah opened a rich vein that Luke could mine as he told his story.
Luke identified the mother of John the Baptist as a member of the priestly family of Aaron and gave her the name Elizabeth. This name, Elisheba in Hebrew, appears only once in the Jewish scriptures. There she is the wife of Aaron and thus the sister-in-law of both Moses and Miriam (which is, of course, the Hebrew spelling of Mary). Playing on that theme, Luke suggests that since Mary and Elizabeth are sisters-in-law, John and Jesus are perhaps cousins.