Where does “Bava Metzi'a” come from?

Bava Metzi'a (English) comes from Aramaic בבא מציעא, from Aramaic בָּבָא, from Yiddish באָבע — granny, grandmother.

Ancestry of “Bava Metzi'a”, step by step

Step	Language	Word	Meaning
1	Aramaic	בבא מציעא	—
2	Aramaic	בָּבָא	gate
3	Yiddish	באָבע	granny, grandmother