From nadab; properly (abstractly) spontaneity, or (adjectively) spontaneous; also (concretely) a spontaneous or (by inference, in plural) abundant gift -- free(-will) offering, freely, plentiful, voluntary(-ily, offering), willing(-ly), offering).
see HEBREW nadab
H5071. nedabah
נְדָבָה noun feminine voluntariness, freewill-offering; — absolute ׳נ Exodus 35:29 14t.; construct נִדְבַת Deuteronomy 16:10; plural נְדָבוֺת Amos 4:5; Psalm 68:10; נְדָבֹת 110:3; construct נִדְבוֺת 119:108; 2 Chronicles 31:14; suffix נִדְבֹתֶ֫יךָ Deuteronomy 12:7 4t. suffixes; —
1voluntariness נְדָבָה אֹהֲבֵם Hosea 14:5 I (׳י) will love them freely; חֵילֶ֑ךָ בְּיוֺם נְדָבֹת עַמְּךָ Psalm 110:3 thy people will be (all) voluntariness in the day of thy host (be ready to volunteer, see BrMP 133); נדבות גֶּשֶׁם 68:10 generous (copious) rain; בנדבה Psalm 54:8 voluntarily, and adverb. accusative נדבה Deuteronomy 23:24 (see Dr.).
2 freewill, voluntary, offering:
a. including gifts used in erection and furnishing of tabernacle Exodus 35:29; 36:3 (P); for first temple 2 Chronicles 31:14, second Ezra 1:6; 8:28.
b. including עולה and שׁלמים Ezekiel 46:42; probably also Amos 4:5, פִי נדבות Psalm 119:108.
c. usually a זֶבַח for festival meals at Passover 2 Chronicles 35:8, Pentecost Deuteronomy 16:10, Tabernacles Ezra 3:5 (besides the ritual offerings); distinguished from נֶדֶר votive offering Leviticus 7:16; Numbers 15:3; 29:39 (P), Leviticus 22:18, 21, 23; 23:38 (H), Deuteronomy 12:6, 17. — (Verbs used are נ ׳הביא Exodus 35:29; 36:3; נ ׳הקריבLeviticus 22:18; נ ׳עשׂה Numbers 15:3; Ezekiel 46:12; נ ׳נתן Leviticus 23:38; Deuteronomy 16:10.)