Picture something wrapped round a thing so that what wants to get out, or in, is held back and comes through soft. That is what muffle does, and a muffler is simply the object that does it. Wrap it round a neck and the cold is what gets held back. Put it in a pipe and the bang of an engine is what gets held back. In both cases nothing is stopped completely; it is just quietened and on its way through.
muffler 可以想成「把東西厚厚地裹起來的那個東西」。裹住之後，想跑出來或想鑽進去的東西就被擋了一下，穿過來的時候變得軟、變得悶。裹在脖子上，被擋住的是冷空氣；裝在排氣管上，被擋住的是引擎的爆裂聲。兩邊都不是完全阻斷，只是讓通過的東西變得溫和一點。
From the word’s history
The source analyses muffler as muffle plus -er, that is, the thing that muffles.
本批評證把 muffler 分析成 muffle（包住、悶住）加上 -er（做這件事的東西），也就是「負責把東西悶住的那一個」，正好就是上面那個畫面。
Wiktionary entry for muffler supplied in this packet (kaikki:3f6f69a190036ae4:263504957:20362), etymology_text: From muffle + -er.
登入就可以看每一支怎麼連回核心畫面。