What is the term given by Jan Breman to migrant workers?

The correct option is Foot loose labour.

Jan Breman, a prominent Dutch sociologist, extensively studied the lives of informal and migrant workers, particularly in India.
He coined the term "footloose labour" to describe these migrant workers who are not tied to any single employer or location. Because of poverty, landlessness, and a lack of secure employment in their native villages, these workers are forced to constantly move from one place to another and from one job to another in search of livelihood.

The term vividly captures their state of constant mobility, precariousness, and the lack of permanent roots or security in the informal economy, making them literally "footloose" as they drift between rural and urban labor markets.