“And Look!” This record of the Canaanite woman is also in Mark 7:24-30. The Greek word translated “look” is idou (#2400 ἰδού), and it is used to get our attention. See commentary on Matthew 1:20 (“Look!).
“Son of David.” “Son of David” is a messianic title. It is unknown how this Canaanite woman came to know that Jesus was the Messiah, but she did. God reveals the truth to people who are humble and hungry (see commentary on Matthew 1:1).