This term comes from molecular gastronomy:
Want to show all your foodie friends that you're really in the know? Then it's time to master the art of making edible dirt. Chefs out there are finding ways to take various foodstuffs and dry, char, and combine them to give the appearance of actual dirt—only with a rich, savory taste.

https://food-hacks.wonderhowto.com/how-to/make-dirt-you-can-...

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As this trend of “food as naturalistic art” takes hold in upscale restaurants around the country, you’ll find lots of new ingredients slipping onto upscale menus: White acorns; tips of fir needles; “dirt” made of dried and crumbled mushrooms, pumpernickel breadcrumbs, black olives, bulgur wheat, or sprouting grains; aloe vera, eucalyptus leaves, chickweed, wild ginger, wood sorrel, yarrow, pineapple weed, and sumac. Dirt is so hot that Crenn cooks her potatoes in the stuff before washing them clean. You’ll find a similar plating style at just-opened modernist Korean eatery Jung Sik Dang in New York, where you’ll need to bring lots of money. Next up: Dessert assemblages growing out of chocolate “humus” (as in dirt, not as in chick peas).
https://www.huffingtonpost.com/rozanne-gold/chocolate-dirt-i...