Proof (δοκιμη). Tests as of metals as in 2. Corinthians 2:9.

Abundance (περισσεια). Late word from περισσευω, to overflow.

Their deep poverty (η κατα βαθους πτωχεια αυτων). Πτωχεια is old word from πτωχευω, to be a beggar, as of Jesus in 2. Corinthians 8:9 (from πτωχος, cowering in fear and poverty, as in Luke 14:13, but ennobled by Christ as in Matthew 5:3; 2. Corinthians 8:9). Poverty down deep. Strabo (LX 419) has κατα βαθους, down to the bottom.

Liberality (απλοτητος). From απλους, single, simple (Matthew 6:22). "The passage from single-mindedness or simplicity to liberality is not quite obvious" (Plummer). Perhaps "heartiness" supplies the connecting link. See also 2. Corinthians 9:11-13.