If you want to get an idea of what adolescents think a word sounds like it should mean, go to UrbanDictionary.com. You may get real definitions there, but you will certainly also get various instances where some juvenile has seen the word and decided to make his mark on it like a dog pees on a fire hydrant. The Urban Dictionary definitions for scumble are quite unsurprising:
1. “To unintentionally trip or fall headlong into something disgusting (stumble + scum).” (9 thumbs up)
2. “The words fumble and scramble together … Only happens in football (or Pro Evo) when somebody ‘fumbles’ the ball in the box and when there is a ‘scramble’ for the ball so a scumble is formed” (11 thumbs down)
3. “Scum + crumble. Scumbles are gross (unknown) crumbs of goo. Unlike a cookie crumb, which isn’t disgusting.” (2 up, 14 down)
Now, of course, among adults, one might, on seeing a new word, consider the context and perhaps even look it up. But even then it is true that with a word such as this one, the form of it may remain as a sort of surface layer that is only half-scraped away to reveal the lexicalized sense. The form is, after all, fairly obtrusive.
There are several parts that give the phonaesthetic impression with this word. There’s the sc (/sk/) onset, which may connect to surfaces that can be scraped, or the scraper or the result – skin, skim, scalp, scrape, scale, scalpel, scallop, sculpt – and the tumbling, crumbling, rumbling, rambling /mbl/ ending, with the dullness of the mid-central vowel in the middle. Beyond that, it has the echoes of scum and stumble, as the kids say, plus fumble, scramble, crumble, and assorted others that it somewhat kinda resembles. For me, the scum echo is not as strong as those of humble and stumble and crumble. But your results may vary.
As it happens, scum appears to be the source, along with the frequentative le suffix. Scum (verb) means to skim the scum (noun) off the surface of something. (Scum (noun) has always meant what it means.) But what scumble refers to is a painterly technique whereby a layer of opaque or semi-opaque paint (usually lighter in colour) is scraped or dry-brushed thin over the layer below to create a softening blending effect. (See a demonstration at www.youtube.com/watch?v=mgWn5A8xRyE.)
You’ll often see this word in inflected forms: scumbled or scumbling. You’ll usually see it in literal use. But it has a certain mouthfeel to it, a certain texture of sound, that invites broader, more figurative use in literary fiction as well. A Nabokov might use it, with his feel for the lusciousness of the language: “The summer tan … would scumble, I knew, the liver spots on my temples.” (Look at the Harlequins) Or perhaps Philip Pullman (The Amber Spyglass): “The moon was brilliant, the path a track of scumbled footprints in the snow, the air cutting and cold.” Or, or, or. If you write fiction, the odds are now pretty good you’ll use it sometime, too. It’s a word as delicious as shortbread, and yet with that tangy pong of paint: a gallery opening right there on your page, giving a glow with your story shining shyly through.