Probably from an unused root meaning to gather in; a granary -- garner.
H4200. mazu
[מָ֫זוּ] noun masculine garner (on formation compare Ol§ 144 b, 197 b) — only Plural suffix מְלֵאִים מְזָוֵינוּ Psalm 144:13 our garners are full (word inflected as if מְ were radical; compare Oll.c.
I. זוז (Late Hebrew זוז move, Assyrian zâzu, move, rise come forth compare COT gloss.; also be agitated, enraged, VR:64, i, l. 11).