Boyd’s Bible Dictionary:
Kings used them
(2 Chron. 9:18). God’s footstool (1 Chron. 28:2; Psa. 99:5).
Concise Bible Dictionary:
The usual accompaniment of a throne (2 Chron. 9:18). The earth is the footstool of God's throne in the heavens (Isa. 66:1; Matt. 5:35). It is symbolical of “the place of rest:” David had it on his heart to build a house of rest for the ark of the covenant of the Lord, and for the “footstool” of God, wherein God could find rest among His people, and where He was to be worshipped (1 Chron. 28:2; Psalm 99:5). It is also symbolical of “subjection to power:” the Lord Jesus must reign until all His enemies are made His footstool (Psa. 110:1; Matt. 22:44; Acts 2:35; Heb. 1:13).
Strong’s Dictionary of Greek Words:
Meaning:
a primary word; a "foot" (figuratively or literally)