One way to hold this word: something has right outside the line that marks what is normal. There is a standard for how big a problem usually is, or for what people usually do to each other, and this thing is somewhere past it. That is why the word feels heavy in every use — it is always reporting that the ordinary measure no longer fits.
The source traces enormity through Latin ēnormitās to ēnormis, which is e- (out, away) plus nōrma (a standard or norm). The literal idea is out of the norm, and both modern senses are that same idea pointed in different directions.
字源資料把 enormity 追到拉丁文 ēnormitās，再往前是 ēnormis：e-（出、離開）加上 nōrma（標準、常規）。字面就是「離開了標準」。今天的兩個意思其實是同一個概念指向不同方向：一邊是大小、嚴重程度超出常態，一邊是行為超出做人的界線。這也解釋了為什麼這個字永遠帶著份量。
Wiktionary (kaikki extract, source_ref kaikki:3f6f69a190036ae4:707437680:14269): "from Latin ēnormitās ... from ēnōrmis ... derived from e- ... + nōrma (norm, standard)"
Two branches
超出常態的規模與嚴重程度
把「超出常軌」用在尺度上：大小、嚴重、難度都不在平常的範圍裡。
noun · C1
How very great something is — its size, its seriousness, or how hard it is to deal with. It is used about a problem, a task, an event or an act, and it says the thing is far beyond the ordinary.
嚴重程度、巨大
超出做人界線的行為
同樣是「跨出那條線」，只是這次那條線畫的不是大小，而是人與人之間可以做到哪裡。
noun · C1
A very cruel or evil act — something so wrong that it goes far past what people will accept.
暴行、極惡之事