Take silence and add -er, the ending English puts on the thing that does a job: opener, heater, cooler. A silencer is simply the thing whose job is to turn the noise down. The word does not care what it is fitted to — the end of a gun, the exhaust pipe of a scooter, even a stretch of DNA — and in every case the name promises more than the thing delivers: it quiets, it does not truly silence.
The source gives the formation directly: silence + -er, with -er traced back through Old English -ere. There is no separate story to tell; the meaning is visible in the parts.
來源資料直接給出它的組成：silence 加上 -er，而 -er 這個字尾可以一路追到古英語的 -ere。它沒有另外的故事，意思就寫在零件上。
Wiktionary entry 'silencer', etymology tree 'From silence + -er' (packet evidence kaikki:3f6f69a190036ae4:1187572892)
From the picture
讓基因不出聲
可以想成把「讓它安靜」從聲音搬到別的東西上。生物學家要描述一段會把鄰近基因壓住的 DNA 時，直接借了同一個字——基因沒有被破壞，只是被壓著不出聲，這和消音器對聲音做的事是同一個動作。這是一條意義上的延伸，不是新的字源。
noun · C2
In the study of genes, a short piece of DNA that stops a nearby gene from being used, or greatly reduces how much it is used.
沉默子（基因）
noun · B2
A tube fitted to the end of a gun so that it makes less noise when it is fired.
消音器
noun · B2
The part joined to the exhaust pipe of a car, bus or motorbike that makes the engine sound quieter. This is the British word; American English calls the same part a muffler.
消音器（排氣管）