A Hebrew expression that means “Save, please.” It comes from Psalm 118:25: "O LORD, save us, we pray."
Psalm 118 is a statement of trust in the Lord’s help. People say this when they need it. The whole psalm was part of a longer song called the Hallel. People sang it on important days. Verse 25 was used in the Jewish Feast of Tabernacles or tents. When this verse was read, people would wave branches of myrtle, willow, and palm trees. People may have waved branches at other times too as a way to show joy. This happens in 2 Maccabees 10:6–7, at a ceremony to make the temple holy again after it had been misused.
The crowd welcomed Jesus to Jerusalem by shouting “Hosanna” (Matthew 21:9; Mark 11:9–10; John 12:13). Then they said, “Blessed is he who comes in the name of the LORD” (Psalm 118:26). This means the crowd was greeting Jesus as the Messiah (God's chosen one).
Even before Jesus’s time, people thought the phrase “blessed is he who comes in the name of the Lord” referred to the Messiah. And it is possible that the word “Hosanna” by itself meant something about the Messiah.
Other things people said when Jesus entered Jerusalem support this idea. In Matthew 21:9, Jesus is called the “Son of David.” In Mark 11:10, there is talk about “the coming kingdom of our father David.” In John 12:13, Jesus is called “the King of Israel.” All of these words suggest Jesus is the Messiah.
We do not need to think that when shouting “Hosanna” the people were thinking about being freed from their rulers. They probably did not know how Jesus would save them. The most we can say is they believed Jesus was sent by God to save them. If there had not been something in their praise that Jesus saw as good worship, he probably would not have accepted it. Only later, when he died and came back to life, would people understand what it really meant for Jesus to be the Messiah.