掃的人或掃的機器
最直接的一家：實際在清地面的人或器具。
noun · B1
A person or a machine that sweeps, that is, that brushes dust, dirt or leaves off a floor, a street or another surface.
清掃者；掃地機
核心畫面
Think of the one who takes care of whatever is left. Sweep is the action and -er is the one who does it, and because -er covers both people and machines, a sweeper can be a worker with a broom or a truck with brushes underneath. Hold on to the idea of what is left over and the football use follows: the player behind everyone else, dealing with whatever got past the rest.
sweeper 可以想成「負責把剩下的東西清乾淨的那一個」。sweep 是掃，-er 是做這件事的人或東西，而 -e…更多收起
sweeper 可以想成「負責把剩下的東西清乾淨的那一個」。sweep 是掃，-er 是做這件事的人或東西，而 -er 兩邊都能指，所以它可能是拿掃把的人，也可能是底下裝著刷子的掃街車。抓住「剩下的交給他」這個感覺，球場上的用法就接得上：站在所有人後面的那個球員，處理的正是前面漏掉的球。From the word’s history
Wiktionary records sweeper from Middle English swepere, equivalent to sweep + -er, with a Middle Low German cognate used for a broom. The -er that covers both a person and a tool is there from the start.
字典記載 sweeper 來自中古英文 swepere，也就是 sweep ＋ -er，並提到中古低地德文的同源字指的是掃除用的掃帚。「人和工具共用同一個 -er」這件事從一開始就在，所以今天它既能指人，也能指機器。
Wiktionary entry for sweeper, packet etymology_text: "From Middle English swepere, swepare, equivalent to sweep + -er."
Two branches
在最後面把剩下的收掉的人
同一個角色搬到球場上：不是清地面，而是清前面漏掉的球。
noun · B2
In football, a defender who plays behind the other defenders, as the last player in front of the goalkeeper.
清道夫（後衛）