Upon the completion of her first knitted sock, Bonne Marie Burns asks “what the heck does *gusset* mean anyway?”
gusset n. A triangular piece of material let into a garment to strengthen or to enlarge some part, esp. in order to afford ease in movement.
One of the usage examples they offer is splendid:
c1570 Pride & Lowl. (1841) 35 The woman and the wench were clad in russet..worne so very neere, That ye might see cleane through both sleeve and gusset The naked skinne.