peat
PEET
Partially decomposed plant material — mostly sphagnum moss, sedges, and grasses — that accumulates in waterlogged, oxygen-poor conditions where the rate of plant growth exceeds the rate of decay. Peat builds up slowly, roughly a millimeter per year, and peatlands thousands of years old can be meters deep. Peat is a carbon vault: the world's peatlands store twice as much carbon as all the world's forests combined. It is also, when dried, a fuel — burned for heat across Ireland, Scotland, Scandinavia, and Russia for centuries. Peat is time made substance: every handful is centuries of compressed growth.
Etymology
Probably from Celtic — compare Scottish Gaelic mòine and Welsh mawn for peat or turf. The English word may derive from a Pictish or Brythonic source. In use since at least the 12th century.
Notes
Peat bogs are also extraordinary archives — anaerobic conditions preserve pollen, seeds, wooden tools, and occasionally human bodies (the "bog bodies" of northern Europe) for millennia.
*
Surprise Me With a Word