What does Mark 11:9 mean?
Although most of the book of Mark is written in Greek, there are some Aramaic words (Mark 5:41; 7:34). Hosanna is a Hebrew term. It's a cry of praise or a prayer for salvation. To come "in the name of the Lord" is to come in God's authority, with His permission and purpose. These two phrases are each the first phrases of Psalm 118:25 and 26, respectively. This is known as the thanksgiving Psalm. The people are—correctly—celebrating that the Jewish Messiah has finally arrived, but they assume—incorrectly—His purpose is to rescue Israel from the Roman oppressors.This event must have been confusing and nerve-wracking for the religious and secular leaders. News of Jesus' miracles and teaching has spread, particularly the resurrection of Lazarus (John 12:9–11). The scribes of Jerusalem had joined with the supporters of Herod Antipas early on to destroy Jesus (Mark 3:6). The Pharisees and chief priests want to arrest Him (John 11:57). Herod wants Jesus dead in a vague, noncommittal way (Luke 13:31; see: Luke 23:8). And Pilate knows that if Jesus or anyone else incites another Jewish rebellion, he will lose his job.
From a secular, political perspective, Jesus' ministry has been a source of concern. The more popularity He has, the more concerned various groups are over unrest or violence. Now, Jesus comes riding into Jerusalem surrounded by a mob celebrating that He has come to re-establish the kingdom of David (Mark 11:10). It's no exaggeration to say the triumphal entry accelerates the plans to kill Jesus: this event clearly establishes Him as a "problem" which will never go away.
John is much more specific about who these "many" are. Some had seen Jesus raise Lazarus from the dead, while others have heard their account and are curious (John 12:17–18). Others have just come for Passover and hear that Jesus is there (John 12:12).
Meanwhile, the Pharisees lament to each other that the world is more interested in Jesus than their rigid, legalistic rules. In fact, the Pharisees confront Jesus, telling Him to control His disciples (Luke 19:39). "He answer[s], 'I tell you, if these were silent, the very stones would cry out'" (Luke 19:40).