Earthiness is a flavor defect deriving from careless, primitive processing that in some contexts may be seen as virtues. Some Harrar coffees sold in specialty stores may have a hint of wildness or earthiness to them. Roasters from Italy often like to include some earthy-tasting Brazilian coffees in their espresso blends. If a New Orleans blend is at all authentic it also should have some Brazilian wildness in it. If the earthy taste dominates to the point that the coffee tastes distinctly sour or harsh, this quality becomes a flavor defect; you won't find such coffees in specialty stores. Your Sumatran sample may have a hint of earthiness or mustiness to it, but it shouldn't.
An odor taint in the coffee beans that produces a dirt-like taste sensation. Results when fats in the coffee beans absorb organic materials from the ground in the drying process during harvesting. Also referred to as dirty and groundy. The undesirable odor and taste of freshly turned soil is found in low-graded batches. Due to poor preparation conditions and botanical origins of the green coffee. Reminiscent of potato flavor also found in instant coffees.