staple

Concise Oxford English Dictionary © 2008 Oxford University Press:
staple1

▶noun

• 1 a small flattened U-shaped piece of wire used to fasten papers together.

• 2 a small U-shaped metal bar with pointed ends for driving into wood to hold electric wires, battens, etc. in place.

▶verb secure with a staple or staples.

– origin OE stapol, of Gmc origin.

Concise Oxford English Dictionary © 2008 Oxford University Press:
staple2

▶noun

• 1 a main or important element of something.

• 2 the fibre of cotton or wool considered with regard to its length and fineness.

• 3 historical a centre of trade in a specified commodity.

▶adjective main or important.

– origin ME: from OFr. estaple ‘market’, from Mid. Low Ger., MDu. stapel ‘pillar, emporium’; rel. to staple1.