The word is built the plain way, ear plus piece, so one way to hold it is: the part of a thing that ends up at your ear. Put your finger on the top of your ear and whatever sits there gets this name — the little speaker pushed into the opening, the rounded end of a telephone pressed against it, the thin arm of your glasses hooked over it. The name comes from the place, not from the job, which is why two of these carry sound and one carries nothing at all.
From the word’s history
The source gives the make-up directly: from ear + piece. The word says where the part sits, and every use follows from that one location.
來源直接寫出組成：ear 加上 piece。這個字說的是「位置」，三個用法都是從同一個位置長出來的，只是各自做著不同的事。
Wiktionary (kaikki extract, source_ref kaikki:3f6f69a190036ae4:1451871389:9178): "From ear + piece."
登入就可以看每一支怎麼連回核心畫面。