A cabbage pod is called

A cabbage pod is called Siliqua.
A silique or siliqua (plural siliques or siliquae) is a type of fruit (seed capsule) having two fused carpels with the length being more than three times the width.
Siliqua is the type of fruit present in the mustard family Brassicaceae. It is a type of dry fruit that separates into two or three segments at maturity. These segments are called valves. An example of siliqua is cabbage, as cabbage also belongs to the Brassicaceae family.