Ramban, on Gen 25:3

“Jecsan also begot Saba and Dadan. The children of Dadan were Assurim, and Latusim, and Loomin.”

“ASSHURIM, AND LETUSHIM, AND LEUMMIM. Rashi comments: “These were the names of clan chieftains. But I cannot reconcile Onkelos’ translation with the language of the text.” as meaning “camps,” Letushim as “owners of tents who spread about in all directions,” and Leumim as “islands” or “sea-districts.” Upon this Rashi comments that he cannot make Onkelos’ translation fit in exactly with the words of the text. Ramban now proceeds to explain Onkelos’ understanding on the verse and also the reason why he was forced to make this translation. It appears to me that Onkelos was of the opinion that Asshurim means camps, companies that travel the roads from city to city, just as it says, a company of Ishmaelites. Onkelos thus considered Asshurim as being derived from the expressions, To His steps (‘ba’ashuro’) hath my foot held fast; His steps (‘ashurav’) do not slide. And Onkelos’ opinion of Letushim is that they are the ones who dwell in tents that are scattered over the face of the earth, resting today in one place and tomorrow in another, for the letter lamed and nun interchange in many places, [thus Letushim would be like Netushim (scattered ones)] just like lishchah and nishchah, [both of which mean “chamber”]; And on that day men were appointed over ‘haneshachoth’ (the chambers)., 12:44. From this root is derived the expression, a sword ‘netushah,’ which is the same as letushah (sharpened). And of the word Le’ummim Onkelos said ulenagvon, [which is Aramaic for the Hebrew word] iyim (islands). Onkelos was stirred to this translation by the word hayu [and the children of Dedan ‘hayu’ (were) Asshurim, and Letushim, and Leummim], when it would have been proper to express it similarly to the verse, And Mitzraim begot Ludim, and Ananim, and Lehabim, and Naphtihim. And in Bereshith Rabbah we find: “Rabbi Shmuel the son of Rav Nachman said that even though we translate these names and say, ‘Merchants, flaming ones, and heads of peoples,’ all of them were heads of peoples.” The matter is as I have explained. The translators rendered Asshurim as “merchants, those who walk the road.” From the word Letushim (sharp, shiny) they derived “men of wickedness,” their faces are faces of flame, burning as torches, from the roots: to sharpen ( liltosh ) his plowshare, and his coulter; He sharpened ( yiltosh ) his eyes upon me. But Rabbi Shmuel the son of Rav Nachman said that even though they are accustomed to thus translate these names, they are still only the proper names of the heads of people, there being no descriptive name among them at all. And such is the case.”

Imported from an open dataset — not yet checked against the printed edition.