The word Zion occurs over 150 times in the Bible. It means “fortification.” In the Bible, Zion is both the city of David and the city of God. The first mention of this word in the Bible is 2 Samuel 5:7, “Nevertheless, David captured the fortress of Zion, the City of David.” Therefore, the city was originally the name of the ancient Jebusite fortress in the city of Jerusalem. After David captured “the stronghold of Zion,” it was then called “the City of David” (1 Kings 8:1; 1 Chronicles 11:5; 2 Chronicles 5:2).
When Solomon built the temple in Jerusalem, this word expanded in meaning to include the temple and the area surrounding it “I have installed my king on Zion, my holy mountain” (Psalm 2:6; 48:2, 11-12; 132:13). This word was eventually used as a name for the city of Jerusalem, the land of Judah, and the people of Israel (Isaiah 40:9; Jeremiah 31:12; Zechariah 9:13).
This word also carries a spiritual meaning. In the Old Testament, this word is used figuratively of Israel as the people of God “and will call you the City of the Lord, Zion of the Holy One of Israel” (Isaiah 60:14). In the New Testament, this word refers to heavenly Jerusalem (Hebrews 12:22; Revelation 14:1) and the body of Christ “See, I lay a stone in Zion, a chosen and precious cornerstone, and the one who trusts in Him will never be put to shame” (1 Peter 2:6).
The Lord promised that at the end of time, this city will be intimately restored to God. And “Also the sons of those who afflicted you shall come bowing to you, and all those who despised you shall fall prostrate at the soles of your feet; and they shall call you The City of the Lord, Zion of the Holy One of Israel” (Isaiah 60:14).
Source: https://bibleask.org/biblical-meaning-zion/