Probably from nagaph (through the idea of impending); a cover or heap; i.e. (only plural) wings of an army, or crowds of troops -- bands.
see HEBREW nagaph
H102. agaph
[אֲגַף] noun [masculine] band, army (loan-word, originally wing of army; Assyrian agappu, Aramaic אגף, wing. Others, from גפ֩ף, Sta§ 256 b) — All Ezekiel & all plural (or dual ?) אֲגַמֶּיךָ Ezekiel 38:9; 39:4; אֲגַמָּיו 12:14 3t; אֲגַמֶּיהָ 38:6 (all with כָּלֿ except 38:22) — bands, armies of king of Judah 12:14; 17:21; hordes (RV) of Gog 38:9, 22; 39:4; specifically of גֹּמֶר 38:6; of תּוֺגַרְמָה ib.