突然重重挨一下：壞運氣
這一層直接承接 wham 的聲音：事情砸下來，人被打得往後退一步。
noun · C1
A sudden, hard piece of bad luck that knocks you back; a serious setback.
重擊；突如其來的打擊
核心畫面
Say wham out loud and you have already got the word: something lands hard, fast, and out of nowhere. A whammy is one of those hits, given a name. Usually the hit is bad luck, and usually it arrives with a friend, which is why the double whammy is the form everyone knows. Sometimes the hit is aimed on purpose, like a curse. And on an electric guitar, the thing that gets hit is the note itself.
把 wham 念出聲，這個字的畫面就到了：有東西又快又重地撞上來，而且毫無預告。whammy 就是把那一下取了名字。…更多收起
把 wham 念出聲，這個字的畫面就到了：有東西又快又重地撞上來，而且毫無預告。whammy 就是把那一下取了名字。撞上來的多半是衰事，而且很少單獨來，所以大家最熟的形式是 a double whammy。有時候那一下是有人故意朝你丟的，像一道咒。至於電吉他上，被撞歪的不是人，是那個音本身。From the word’s history
Whammy is wham plus the ending -y, so the sound of a sudden hard hit is built into the word.
whammy 由狀聲詞 wham（猛力撞一下的聲音）加上字尾 -y 組成，所以「突然重重挨一下」這個感覺是從聲音直接長出來的，不是後來才附加的比喻。
Wiktionary etymology for whammy: "From wham + -y." (kaikki:3f6f69a190036ae4:859810356)
Three branches
有人朝你丟的那一下：咒
同樣一下，差別在於這次有人瞄準了你——不是運氣不好，是被下了咒。
noun · C1
To use magic, or to pretend to, so that someone has bad luck. The dictionary marks this use as American English.
下咒；施法讓人倒楣
被撞歪的是聲音：吉他搖桿
還是那一下，只是這次挨打的不是人而是音高；效果很誇張，所以沿用了同一個狀聲詞。
noun · C1
The metal lever on an electric guitar that you push or pull to make the note bend up and down; also the whole system in the guitar that does this.
（電吉他的）搖桿