A vocabulary of landscape — a landscape of words 1054 entries

duff

DUF
The layer of decomposing organic material on the forest floor — fallen leaves, needles, bark fragments, and other debris in which the original plant parts are no longer individually recognizable. Duff is the transition between litter (freshly fallen material you can still identify) and soil (fully decomposed organic matter).
Etymology
Possibly from a dialectal English word for dough — the soft, dark, half-finished material underfoot. Also possibly from Old Norse.