The Greek adjective authairetos is formed from autos (self) and haireō (to choose). It means self-chosen, voluntary, or acting of one's own accord — without compulsion, pressure, or obligation. Action arising purely from free choice of the will. It appears twice in Paul, both times describing the extraordinary generosity of the Macedonian churches.
In 2 Corinthians 8:3 and 8:17, Paul uses authairetos to describe completely voluntary giving — the Macedonians gave 'of their own accord,' and Titus went 'of his own initiative.' True Christlike giving and service cannot be coerced; it must spring from inner transformation. God loves a cheerful giver (2 Corinthians 9:7) — one who gives because they freely choose to.