From rabab; abundance (in number), i.e. (specifically) a myriad (whether definite or indefinite) -- many, million, X multiply, ten thousand.
see HEBREW rabab
H7233. rebabah
רְבָבָה noun feminine multitude, myriad, ten thousand (Köii.1.221); — absolute ׳ר Genesis 24:60 +; suffix רִבְבָתוֺ Kt 1 Samuel 18:7 2t. (Qr רִבְבֹתָיו); plural absolute רְבָבוֺת 18:8 construct ִרבְבוֺת Micah 6:7 +, ִרבֲבוֺת Deuteronomy 33:17; suffixsee above Qr; — myriad 10, 000: of great number of person, indefinite Genesis 24:60 (J; רְבָבָה אַלְפֵי thousands of myriads), Deuteronomy 33:2(poem; קֹרֶשׁ מֵרִבְבוֺת, but see קֹרֶשׁ, near the end). Psalm 3:7; ct 5:10; תִשׂ אַלְפֵי ׳ִרבְבוֺת Numbers 10:36, compare Deuteronomy 33:17 (poem); — רְבָבָה Ezekiel 16:7 read ᵐ5 רְבִי Co Berthol Krae; — more precisely(100, 1000), 10, 000, Judges 20:10; opposed to 2, Deuteronomy 32:30 (poem), opposed to 100, Leviticus 26:8 (H), opposed to 1000, 1 Samuel 18:7-8, 21:12; 29:5; Psalm 91:7; so of things, Micah 6:7.