What is the meaning of "hawari" (disciple/supporter) of the Prophet, and why was Az-Zubair ibn Al-Awwam the hawari of the Prophet, may Allah's peace and blessings be upon him?

Al-Zubayr ibn Al-Awwam is the cousin of the Prophet Muhammad, peace and blessings be upon him, and his "Hawari" among his community. The meaning of "Hawari" is: my supporter and my special one among my companions, because he was among the closest and most devoted to him. He was among the first to embrace Islam, and one of the ten promised Paradise.