蹭出來的髒痕（名詞）
這就是核心畫面本身：被抹開、邊緣糊掉的那一塊。
noun · B2
A dirty mark left on a surface when something soft, wet or greasy — ink, chalk, make-up, a dusty finger — is rubbed across it, so the mark has blurred edges instead of a clean shape.
髒污痕跡
核心畫面
Picture soot on a finger, and then the finger dragged across a page. Nothing about the result has a clean edge: the black spreads sideways, the writing underneath goes cloudy, and you cannot say exactly where the mark stops. That softness of edge is what smudge names. Hold the picture and the verb follows at once, because the verb is simply the rubbing that makes it, either done to a thing or happening to a thing. The word has a second, smokier side too. Thick smoke has no edge either: it spreads, it drifts, it settles on whatever it reaches. English gives that cloud the same name, and the sense of a slow smoky fire, and of a bundle of herbs burned for its smoke, all live on that side.
可以想成手指沾到煤煙，然後往紙上一抹。抹出來的東西沒有一條乾淨的邊：黑色往兩邊散開，底下的字變模糊，你也說不出髒痕到…更多收起
可以想成手指沾到煤煙，然後往紙上一抹。抹出來的東西沒有一條乾淨的邊：黑色往兩邊散開，底下的字變模糊，你也說不出髒痕到哪裡結束。smudge 指的就是這種「邊緣糊掉」的東西。抓住這個畫面，動詞也就跟著出來了，因為動詞說的正是造成它的那個蹭：可以是人去蹭，也可以是東西自己被碰到就糊。這個字還有另一面，畫面偏向煙。濃煙一樣沒有邊：它散開、飄走、沾到碰得到的東西。英文把那團煙也叫 smudge，悶燒的煙堆和為了冒煙而燒的香草束，都掛在這一面。From the word’s history
The supplied Wiktionary entry derives the noun from the verb and calls it a doublet of smutch; the verb goes back to Middle English *smogen, alongside Middle Dutch smoddich and German schmutzig, both meaning dirty. So the idea of dirt sits in the word itself, and the sooty, edgeless mark is the picture it settles on.
資料裡說這個名詞是從動詞來的，而且和 smutch 同源；動詞可以追到中古英語的 *smogen，和中古荷語 smoddich、德語 schmutzig（髒的）是同一群。也就是說「髒」本來就在這個字裡面，而它落腳的畫面，就是那種煤煙一樣、沒有邊的痕跡。
Wiktionary entries supplied in this packet: noun etymology 1 (source_ref kaikki:3f6f69a190036ae4:784276083) and verb etymology 2 (source_ref kaikki:3f6f69a190036ae4:784288716)
Three branches
把東西蹭糊、弄髒（動詞）
同一個畫面往前倒帶一步：先有蹭，才有那塊糊掉的痕跡。受詞選什麼，決定糊掉的是字還是表面。
verb · B2
If ink, writing, make-up, chalk etc smudges, or if you smudge it, it is touched or rubbed before it is dry or fixed, so it spreads sideways and becomes dirty and unclear.
把（字跡、妝）蹭糊
濃煙那一面
跟核心畫面共用同一個性質：沒有邊、會散開、會沾上東西。資料把這些意思和「髒痕」放在同一個字源底下，所以它不是另一條歷史來源，比較像同一個字的另一種樣子。
noun · C1
Thick smoke, or the slow-burning pile of damp wood and leaves that makes it, lit near a house or a tent so that the smoke drives mosquitoes and other insects away; also thick smoke used to treat or clean a place.
驅蟲的濃煙（悶燒堆）