One way to hold this word: something that is pushed down inside or against something else, and passes the push on to whatever is in the way. A hand does the pushing in one group of uses, a machine in the other, but the picture stays the same — a part that travels down a tube or onto a hole, and moves what it finds there.
可以想成一個畫面：有一段東西被往下壓，壓進一個管子裡，或壓在一個洞口上，然後把這股力傳給擋在前面的東西。有些用法是人用手壓，有些是機器自己動，但畫面沒變：一段在別的東西裡面走的零件，把前面的東西推走。
From the word’s history
From plunge plus -er, so the word names the thing that does the plunging: the part that is pushed down.
由 plunge（猛地往下壓）加上 -er（做這件事的那個東西）組成，字面就是「負責往下壓的那一個」。
Wiktionary entry for plunger, supplied in this packet (kaikki:3f6f69a190036ae4:1176334752): 'From plunge + -er.'
登入就可以看每一支怎麼連回核心畫面。