Zuzim in Ham
“Zamzumim – Rabbi Yosei bar Ḥanina said: Intimidating military commanders. Zamzumim is because they would be constantly ready [mezumanim] for battle.” Bereshit Rabbah 26:7
We must first solve a machlokes (dispute) regarding the Zuzim and their connection to the Zamzummin. From Rashi, vis-a-vis the Siftei Chakhamim: “Zuzim. These are the Zamzummim.”1 “These are the Zamzummim. Rashi knows this because it is written here Rephaim and Emim, and mentions the Zuzim with them — while in Devarim 2:11, it mentions Rephaim, Emim and Zamzummim. Thus, Zuzim must be Zamzummim.”2 Rashi's reasoning for the identity comes from a contextual parallel between the two lists, where the Zuzim are absent, and tenuously replaces them with the Zamzummim; this seems probable.
Most references place the Zuzim and Zamzummim alongside both Rephaim and particularly the Emim, but it appears the “Zuzim” disappear in the later references. From Ramban we get confirmation of Rashi’s theory “The Moabites and the Ammonites were the ones that changed [the name of the Rephaim] to other names: [the Moabites calling them] Emim and [the Ammonites calling them] Zamzummim.”3 In other words, the Emim and Zuzim/Zamzummim are the same group (according to Ramban), and both of them were once called Rephaim until the Moabites and Ammonites changed their name respectively. However, this latter point could easily be gleaned directly from the Torah in Deuteronomy which says “[Ammon] is considered a land of Rephaim; Rephaim dwelt therein formerly, and the Ammonites call them Zamzummim.”4
From Ramban we also get information about the Zamzummim “Similarly He further said with reference to [the land of] the children of Ammon that it is of the land of the Rephaim [which G-d gave to Abraham] for that, too, belonged first to the Rephaim. The Ammonites called them Zamzummim, from the expression ‘z’mamo (his evil scheme) do not further (Psalms 140:9), except that [the letters zayin and mem] are doubled [in the name “Zamzummim”], which thus indicates “the people from whom nothing is withheld which they purpose to do.”(Genesis 11:6)5
Bereshit Rabbah gives us another etymology for the Zamzummin “Zamzummim – Rabbi Yosei bar Ḥanina said: Intimidating military commanders. Zamzummim is because they would be constantly ready [mezumanim] for battle.”6 The term obviously relates to warriors, just like the Gibborim, or Nephilim, but implies a potentially more specific role within the military as commanders. Alternatively, one could view them ‘constantly ready for battle’ as a sort of standing army, or at least the most trained, elite warriors in the region who would be ready for any battle. This role could be similar to a “champion” like that of Goliath, who likely trained year round to be always at the ready as a sort of mercenary.
The term “Zuzim” might be slightly different from Zamzummim, referring to “things which move” - in this context, perhaps with an indication of a nomadic group.7 This may explain why the Zuzim 'disappear’ if they shifted from a nomadic group to a settled group preparing for war. A nomadic group being on the fringes of Canaan - specifically in the land of Ammon, or Moab - may have settled down into the region given its periphery to Canaan.
This theory of Ammon can actually be taken deeper by bringing back the original reference to the “Zuzim in Ham”. Where is Ham? The most probable location is somewhere between Moab and Bashan - Og’s territory south of Damascus - at least during the period of the war against Chedorlaomer. The reason for this would come from the identifications for the Emin located in Moab, and the Rephaim - typically associated with Og and Sihon in Bashan and just east of the Jordan - making the logical location of Ammon as the locale for the so-called “Land of Ham”.
It’s important to realize Ammon and Moab, descendants from the sons of Lot, are later polities that do not exist in this period. The etymology of Ammon comes from Lot’s son “ben-Ammi”, but there could be a connection to “Am” and “Ham” implying his son was named as such for his birth in the ‘Land of Ham’.
Ultimately the Zuzim, or alternatively named Zamzummim in their settled form, appear like some sort of nomadic giant group given this name by the people of Ammon. There does not appear to be any critical difference between the Zuzim or the Emim, other than their geographical presence. Nor do the Rephaim - at least those in Bashan and Astaroth Karnaim - appear very different from the Zuzim, but the Zuzim are more of a subcategorization of the Rephaim with a specific name for them in the land of Ammon.
Rashi on Genesis 14:5:4
Siftei Chakhamim, Genesis 14:5:2
Ramban on Deuteronomy 2:20
Deuteronomy 2:20
Ramban on Deuteronomy 2:10
Bereshit Rabbah 26:7
Hebrew word #2104 in Strong's Concordance