Why does it say "Shevi Egypt" and "Galus Kush"?
Malbim: Egypt was not exiled, just captives were taken. Kush was totally exiled.
What is "va'Chashufei Shes"?
Rashi: This is like Chashuf Shes; the Yud is extra, like the Yud at the end of "v'Chorai" (19:9), "[v'Kara Lo] Chalonai" (Yirmeyah 22:14), "[Bahamos] Sadai" (Tehilim 8:8). Shes is the anus, and similarly "va'Yichros Es Madveihem ba'Chetzi Ad Shesoseihem" (Shmuel II, 10:4). This punishment was Midah k'Neged Midah for their ancestor Cham, who saw his father's Ervah and did not cover it.
Radak: Chashufei is like Chashufim. Similarly, "v'Kara Lo Chalonai" (Yirmeyah 22:14, is like Chalonim, and similar verses. Shes (the buttocks) is a euphemism for the Ervah, and similarly "Ad Shesoseihem."
It already said "Arom". Why does it add "va'Chashufei Shes"?
Radak: The disgrace of being naked is that the Ervah is exposed. Similarly, Melech Amon "va'Yichros Es Madveihem ba'Chetzi Ad Shesoseihem" to disgrace David's Sheluchim.
Does "Ervas Egypt" exclude Kush?
Radak: No. It already mentioned also Kush [going naked]. The matter is repeated about Egypt for their great disgrace, like it says about them "Gidlei Vasar", "Asher Besar Chamorim Besaram" (Yechezkel 16:26, 23:20). Malbim - they are called "Eshes ha'Zimah" (ibid., 23:44). Nevi'im always disparaged them for this.
