Amas (עָמַס) means to load, burden, or carry a heavy load. It appears about 9 times in the Old Testament and is used of laden animals, burdens placed on people, and in the powerful Psalm 68:19 where God is the one who 'daily bears our burdens.' The noun massa (burden) is related in concept though from a different root.
Psalm 68:19 is the theological crown of amas: 'Blessed be the Lord, who daily bears us up — the God who is our salvation.' The imagery is of a pack animal bearing a heavy load — except here, God stoops to bear the weight of His people. Isaiah 46:1–4 extends this beautifully: Babylon's idols are carried (nasa) on exhausted animals, but the God of Israel carries Israel — 'I have made you, and I will carry you; I will sustain you and I will rescue you.' The true God is not one we carry; He is the One who carries us.