Strong's H5071נְדָבָה: properly (abstractly) spontaneity, or (adjectively) spontaneous; also (concretely) a spontaneous or (by inference, in plural) abundant gift KJV:free(-will) offering, freely, plentiful, voluntary(-ily, offering), willing(-ly), offering).
Meanings: Brown-Driver-Briggs (1906) and Strong's Hebrew Dictionary (1890), public domain, via the Open Scriptures Hebrew Bible Project (CC BY 4.0). TWOT numbers for reference only.
Root family 1299: נָדַבnādab — incite, impel; whose heart incited; volunteer, offer free-will-offerings; to present spontaneously; offer freely, be willing, be willingly