Where does “chim-” come from?

chim- (Choctaw) comes from Chichewa chi-, from Proto-Bantu kɪ̀- — Class 7 noun prefix.

Ancestry of “chim-”, step by step

Step	Language	Word	Meaning
1	Chichewa	chi-	language prefix; language
2	Proto-Bantu	kɪ̀-	Class 7 noun prefix