Maybe not everyone knows that under-thread component in multi-needle lockstitch quilting and in "schiffli" embroidery is called
cocoon bobbin.
Container which holds the bobbin is called shuttle or schiffli by the embroidery industry.
The yarn is drawn off from the inside to the outside to avoid friction between shuttle and yarn.
A proper thread lubrication is one of the major determinants of the performance of cocoon bobbins.
Especially synthetic threads need proper and accurate lubrication.