Probably from the same as 'aven (in the sense of effort, but successful); ability, power, (figuratively) wealth -- force, goods, might, strength, substance.
see HEBREW 'aven
H202. on
I. אוֺן noun masculine vigour, wealth — absolute Hosea 12:9, suffix אוֺנִי Genesis 49:3 + etc.; plural אוֺנִים Psalm 78:51 +.
1 manly vigour אֶתאֱֿלֹהִים שָׂרָה בְּאוֺנוֺ Hosea 12:4 (of Jacob); אוֺן רֵאשִׁית beginning of manly vigour Genesis 49:3 (of Reuben, first-born of Jacob); Deuteronomy 21:17; Psalm 105:36 (firstborn Egyptians), so 78:51, אוֺנִים רֵאשִׁית where ׳א is assimilated to מִצְרַיִם, or intensive plural
2 strength of man Job 18:7, 12; behemoth 40:16; plural intensive אוֺנִים מֵרֹב Isaiah 40:26 because of the abundance of great strength (of God); of man אוֺנִים אֵין 40:29 one not having strength; אוֺנִים תּוֺחֶלֶת Proverbs 11:7 hope in strength (not the hope of iniquity RV, or of unjust men AV).
3 wealth Job 20:10; Hosea 12:9 א ׳מָצָאתִי לִי ("" עָשַׁרְתִּי).