真的黑灰
這一組就是畫面本身：燒出來的黑粉，以及它留下的一個個黑印。
noun · C1
Dirt or soot — the fine black powder that smoke and burning leave behind — or one small flake or mark of it.
煤灰；一小片黑灰、黑污漬
核心畫面
One way to hold this word: a black mark that comes off on whatever it touches. Soot from a coal fire lands on a window ledge, on a shirt, on the end of your nose, and it leaves a smear. Everything else this word does is that same smear put somewhere new — on a field of wheat, where the ears go black and dusty, and on books and jokes, where the dirt is not real but the speaker means it to sound just as real.
可以想成「一塊會沾到別人身上的黑」。燒煤留下的灰落在窗台上、衣服上、鼻尖上，碰到什麼就在什麼上面留下一道黑印。這個字…更多收起
可以想成「一塊會沾到別人身上的黑」。燒煤留下的灰落在窗台上、衣服上、鼻尖上，碰到什麼就在什麼上面留下一道黑印。這個字其他的用法，都像是把同一道黑印抹到別的地方。抹到麥田上，穗子變成一團黑粉。抹到書和笑話上，髒是假的，但說話的人要你聽起來覺得一樣髒。From the word’s history
From Middle English smutten, 'to defile, debase', related to German Schmutz, 'filth, dirt'. The word begins at dirtying something, and every later use keeps that.
來自中古英文 smutten（弄髒、玷汙），和德文 Schmutz（髒汙）同源。這個字一開始講的就是「把東西弄髒」，後面的每個用法都還留著這件事。
Wiktionary etymology supplied in this packet (kaikki extract, source_ref kaikki:3f6f69a190036ae4:503250317): Middle English smutten “to defile, debase”; cf. German Schmutz, schmutzen; doublet of schmutz.
Three branches
抹到話語和書本上的髒
同一道黑印被搬到抽象的東西上。這是一個比喻，不是說這個意思在歷史上從煤灰長出來；只是兩邊用的是同一個「弄髒」的想法。
noun · C1
Books, pictures, films or talk about sex that some people find dirty and offensive. Someone who calls a thing smut is saying they think it is cheap and unclean, not just that it is about sex.
黃色書刊；下流的內容或言語
作物上的黑粉
這一組回到看得見的黑：真菌讓穀粒變成一團黑粉，手一摸就沾上，樣子和煤灰幾乎一樣，所以沿用了同一個字。
noun · C2
A plant disease of grasses and grain crops, in which certain fungi turn the seeds into a black, dusty mass; also the fungus that causes it.
黑穗病（穀類作物的真菌病害）