The Hebrew noun ezor (אֵזוֹר) refers to a belt, girdle, or waistband — worn around the waist to gather garments and carry weapons. Both functional and symbolic, the girdle represented readiness for action and the identity of the wearer.
Jeremiah wore a linen girdle as an enacted prophecy (Jeremiah 13). John the Baptist's leather belt identified him with Elijah (2 Kings 1:8). Paul's armor of God begins with the belt of truth (Ephesians 6:14). Truth is the foundational garment of the spiritual warrior — to gird oneself is to prepare for holy service or battle.