From an unused root (meaning to collect as water); a marsh; hence a rush (as growing in swamps); hence a stockade of reeds -- pond, pool, standing (water).
H98. agam
אֲגַם noun [masculine] troubled pool (Aramaic id., , Assyrian agammu DlW) — ׳א absolute Isaiah 35:7; construct 41:18 2t.; אֲגַמִּים Exodus 8:1-2t.; אַגְמֵי Isaiah 14:23; אַגְמֵיהֶם Exodus 7:19 —
1 troubled or muddy (gloomy) pools or marshes, plural ׳א מַיִם Isaiah 14:23.
2 any pool, pond, singular ׳א מַיִם Isaiah 41:18; Psalm 107:35; 114:8; plural without מַיִם Exodus 7:19; 8:1 (P) Isaiah 42:15.
3 swamp-reed, rush (= אַגְמוֺן) Jeremiah 51:32.