Waw is the Hebrew letter that the next eight verses start with. Very few Hebrew words start with this letter, but it is often used as a conjunction as "and". The theme of this section is trust in God.
ו
Psalm 119.41Let your steadfast love come to me, O Lord, your salvation according to your promise;
Again David prays to Jehovah, the Lord, the Eternal I Am. He prays for two things, mercy and salvation. They are in some ways synonymous words in this context, because they are all about the same. When God shows mercy, we share in His salvation.