Penēs (G3993) describes the working poor — one who labors to survive but has little to nothing left over. Distinct from ptōchos (the destitute, utterly poverty-stricken beggar), penēs describes the struggling laborer, like a day worker who barely makes ends meet.
2 Corinthians 9:9 quotes Psalm 112:9 — the generous man scatters abroad and gives to the poor. The contrast in 2 Corinthians 8:9 is the theological foundation: 'Though he was rich, yet for your sake he became poor (eptōcheusen), so that you through his poverty might become rich.' Christ identified with every layer of poverty to bring the riches of grace to all who receive Him.