From Old English stapol 'post, pillar' — the U-shaped metal fastener resembled a small post.
A device for fastening sheets of paper together with a small metal staple.
From staple + -er. The fastener called a 'staple' comes from Old English stapol 'post, pillar,' from Proto-Germanic *stapulaz 'pillar.' A staple was originally a U-shaped metal post driven into wood. The office stapler was invented in the late 19th century. Key roots: *steh₂- (Proto-Indo-European: "to stand").