As far as I have been able to establish in my research of the Nusz family heritage, the Nusz name seems to come from a shortened version of Nu▀baum meaning nut tree. The family name may have been taken because they had a nut tree orchard, or because they were the ones that gathered the nuts from the trees for market. The sz seems to be a characteristic spelling used by the German families immigrating from Russia that had the ▀ in their names. By the way, the Russian language doesn't use the ▀. There are spelling variations of Nuss and Nussbaum from the Germans immigrating from Germany during the same time frame that had the ▀. It is quite possible, that while the Germans that emigrated to Russia, continued speaking the German language as they remembered it while they were in Russia, that those remaining in Germany developed a different dialect that failed to emphasize the sz sound of the ▀.
There is another possibility of the use of the sz versus ss spelling usage. In German as you find it written in the older books, there are two styles of the letter s that are used besides the ▀. One appears similar to the modern cursive s and the other looks similar in appearance to a dagger (or perhaps even misunderstood as an f). When the ▀ was translated to another language, the dagger shaped s followed by the z was used. When these two letters were placed side by side, they looked very similar to the ▀. Another possibility is that through the use of the ▀, it transformed into two of the modern cursive s shapes. If you begin to lose focus of your handwriting skills and the fact that you are actually writing the ▀ letter, then it appears that the ▀ is two cursive s's with one on top of the other. If you move them side by side, the ▀ becomes ss in cursive. This would explain how Nu▀ could become either Nusz, or Nuss (or even Nufs).
I must admit however, that the preceding paragraph may only be subjection on my part but I'm willing to admit my error if I find more convincing information to the contrary. In addition to the possibilities presented in the preceding two paragraphs, we also must take into account the spelling variations that may have come about simply by the ports of entry that were used, and the clerks that were doing the transcriptions of names. It may simply have been a clerk hearing a sz sound and another hearing a lingering s (ss) sound and each writing it down differently. Many names were changed as people entered the United States and the spelling differences may have only been caused by such immigration clerk errors.