"Hosanna" is the Greek form of a Hebrew term that means "Save, we beseech thee." This expression appears in Psalm 118.25, which is part of the Hallel sung at the Feast of Tabernacles. It was the cue word at which the worshipers would wave their palm branches in joyous celebration. The waving of branches became a common expression of religious exuberance, not limited to just a set moment in the ritual of the Feast of Tabernacles.
In the Hallel, the word Hosanna is juxtaposed with the phrase "Blessed is he that cometh in the name of the Lord." The high point of the people’s enthusiasm for Jesus occurred as he rode on the colt of an ass into Jerusalem. The people sang "Hosanna" and "Blessed is he that cometh in the name of the Lord," and waved palm branches.