Meaning of STAPLE in English
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 ~ or ~s.
OE stapol , of Gmc origin.
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.
ME: from OFr. e~ 'market', from Mid. Low Ger., MDu. stapel 'pillar, emporium'; related to ~ 1 .
Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004