From the outset of the factory system in woven apparel, after cloth has been laid out and cut in the configurations of patterns for various sizes, the cut parts have been grouped by parts of the garment'fronts, backs, sleeves, patches for pockets, collars'and tied together into bundles for operators, who sew together individual parts'hence the term  bundle system.
The bundle systems gets its name from the way the cut parts are grouped together.