這個拼法是2個不同的字· 2 words spelled “washer”
- 1washer · flat ring under a nut墊圈（華司）A small flat ring, squeezed between two things that are being tightened together.
- 2washer · washing machine洗衣機（口語）Picture the ending -er doing its plain job: it points at whoever or whatever does the action.
washer · flat ring under a nut
nounA small flat ring, squeezed between two things that are being tightened together. Nobody looks at it. Its whole job is to spread the pressure so nothing is crushed, and to fill the last thin gap so that water or air cannot get out. You usually learn it exists only when one wears thin and a tap starts to drip.
washer · washing machine
nounPicture the ending -er doing its plain job: it points at whoever or whatever does the action. Wash plus -er is simply 'the one that washes'. For a long time that one was a person standing over a tub; then a machine took the work, and the word moved across without changing. So the picture holds both: a hand in the water, and a drum turning in the corner of a kitchen, doing the same job.
From the word’s history
From Middle English wasshere, equivalent to wash + -er, with cognates in Dutch wasser and German Wäscher. The ending is the ordinary agent ending, which is why the same word can land on a person or on a machine.
依來源記載，這個字來自中古英語 wasshere，等於 wash 加上 -er，荷蘭語 wasser、德語 Wäscher 是同源詞。-er 就是最普通的「做這件事的人／東西」字尾，所以同一個字可以落在人身上，也可以落在機器身上。
Wiktionary, "washer" (etymology 1)