>>6167863By the latter half of the 15th century, doublets were becoming shorter, exposing the groin which was previously covered by it — a codpiece was a piece of cloth intended to cover the gap between the doublet (shirt) and hoses (tights).
Over the course of the 16th century, it became more prominent, and featured in Jochiam Meyer’s fencing treatise of 1570, the one I based Sira’s weapons and outfit from.