Several biblical encyclopedias indicate that the cry of "Hosanna!" was a cry for salvation. It can be translated "Do save," "Save, we ask" or "Lord, grant salvation!"
That is its sense as it appears in Psalm 118:2. On the Feast of Tents the Jewish people made a procession with palms while singing hosanna. The seventh day was called the Great Hosanna. Used by crowds in the Gospels as Jesus enters Jerusalem (Matthew 21:9; Mark 11:9 ; and John 12:13), it is a cry of praise, homage, supplication, and joy used to recognize Jesus’ royal messianic dignity.
The cry of hosanna passed from use in the liturgy of the synagogues to our use in the Christian liturgy where it continues to be a shout of praise and honor.