One way to hold this word: it is dust plus -er, the thing that deals with dust. Picture a cloth going across a grey shelf and coming away grey itself. Most of the senses are that job in different shapes — a cloth in the hand, a felt block on a , a loose coat taking the dust so your shirt does not, a person hired to do the wiping. And because -er only names the , it can also point the other way: the wind that throws the dust about is a duster too.
From dust plus the agent suffix -er, which comes through Middle English -ere and Old English -ere; the suffix names the one that does the action, whether a person or a thing.
來源把它拆成 dust 加上表示「做這個動作的人或東西」的字尾 -er，這個字尾經由中古英文 -ere、古英文 -ere 一路傳下來。所以 duster 字面上就是「處理灰塵的那一個」，人或工具都可以。
Wiktionary, English entry 'duster' (packet source_ref kaikki:3f6f69a190036ae4:1257841025)
From the picture
替你擋灰的衣服
一樣是處理灰塵，但位置換了：這次不是把灰擦掉，而是先擋在外面，不讓它碰到裡面那套衣服。
noun · B2
A long, loose, light coat worn over your clothes to keep dust off them — either the coat put on for housework, or the long coat once worn for riding and travelling on dusty roads.
防塵長外套、罩衫
做這件事的人
-er 本來就可以指人。同一個字尾，換成人來做這份工作。
noun · C1
A person who dusts — someone whose job or task is wiping dust off surfaces.
擦灰塵的人
自己揚起灰的那陣風
這一支是同一個字尾的另一半：-er 只說「做這個動作的那一個」，沒說方向。於是把灰弄得滿天都是的東西，也拿到了同一個名字。
noun · B2
A dust storm: a strong wind that lifts dry soil off the ground and carries it along in a thick cloud. It is an informal American word.
沙塵暴、土風暴
noun · B1
A cloth used for wiping dust off furniture and other surfaces. It can also be a soft pad, a mitt, or a puffy brush made for the same job.
除塵布、撢子
noun · B1
A block covered with strips of soft felt, held in the hand and used to wipe chalk off a blackboard.
板擦