Historical and economic reasoning”

This means reasoning that draws upon both:

Historical knowledge

What happened?

Serfdom ended.

Wage labor expanded.

Industrialization occurred.

Economic reasoning

How do these developments affect economic organization?

Free labor can be contracted.

Workers can move between employers.

Employers can compete for workers.

Then you connect them:

The removal of inherited labor restrictions facilitated the development of more mobile labor markets.

That is historical and economic reasoning.