gusset

Concise Oxford English Dictionary © 2008 Oxford University Press:
gusset /ˈgʌsɪt/

▶noun

• 1 a piece of material sewn into a garment to strengthen or enlarge a part of it, e.g. the crotch of an undergarment.

• 2 a bracket strengthening an angle of a structure.

– derivatives
gusseted adjective.

– origin ME: from OFr. gousset, dimin. of gousse ‘pod, shell’, of unknown origin.