From an unused root meaning to devour; a kind of locust -- palmer-worm.
Englishman's Concordance
1) locusts Part of Speech: noun masculine collective A Related Word by BDB/Strong’s Number: from an unused root meaning to devour Same Word by TWOT Number: 338a
Brown-Driver-Briggs
גָּזָםnoun masculineAmos 4:9locusts (collective) — absolute גָּזָםJoel 1:4; Joel 2:25; Amos 4:9; — always as devouring, devastating, Joel 1:4 ("" אַרְבֶּה, יֶלֶק, חָסִיל) Joel 2:25 ("" id.); Amos 4:9 alone: your gardens and your vineyards, and your fig-tres and your olive-treesיאֹכַל הַגָּזָם.
Joel 1:4 HEB: יֶ֤תֶר הַגָּזָם֙ אָכַ֣ל הָֽאַרְבֶּ֔ה NAS: What the gnawing locust has left, KJV:That which the palmerworm hath left INT: What the gnawing has eaten the swarming
Joel 2:25 HEB:הַיֶּ֖לֶק וְהֶחָסִ֣יל וְהַגָּזָ֑ם חֵילִי֙ הַגָּד֔וֹל NAS: the stripping locust and the gnawing locust, My great KJV: and the caterpiller, and the palmerworm, my great INT: the creeping the stripping and the gnawing army my great
Amos 4:9 HEB:וְזֵיתֵיכֶ֖ם יֹאכַ֣ל הַגָּזָ֑ם וְלֹֽא־ שַׁבְתֶּ֥ם NAS: [wind] and mildew; And the caterpillar was devouring KJV: increased, the palmerworm devoured INT: and olive was devouring and the caterpillar have not returned
