Why does it say "va'Yim'atu va'Yashochu"?
Rashi: Initially they were lowly and few due to Otzer 1 Ra'ah v'Yagon.
Radak: When Hashem wants, He reverses their situation, when they sinned via haughtiness over their great good - "me'Ra'as Yoshevei Vah" (verse 34). "Va'Yim'atu" is the opposite of va'Yirbu; "va'Yashochu" is the opposite of going upright. Now they will be dark and bent.
Malbim: Sometimes they are diminished and bent due to "Otzer Ra'ah" - an evil kingdom conquers them. They diminish them via killing many, and the remainder bow amidst agony.
Presumably, Rashi, like Radak, explains Otzer to be authority. (PF)
What is "me'Otzer Ra'ah v'Yagon"
Ibn Ezra: Otzer refers to the womb - shutting it is the opposite of va'Yirbu - "Atzor Atzar [Hashem Be'ad Kol Rechem]" (Bereishis 20:18).
Radak: It means me'Otzer v'Ra'ah [v'Yagon]; the prefix Vov is omitted. Otzer is authority of others over them, and they are bent under them. This is like "me'Otzer umi'Mishpat Lukach" (Yeshayah 53:8) and "Yoresh Etzer" (Shoftim 18:7), i.e. authority of the Goyim. They will be bent due to authority, evil and moaning. "Ra'ah" is bodily harm and monetary loss. Yagon is in the heart.