peat (n.) Look up peat at Dictionary.com
c. 1200, in Scottish Latin, of unknown origin, probably from a Celtic root *pett- (source also of Cornish peyth, Welsh peth "quantity, part, thing," Old Irish pet, Breton pez "piece"). The earliest sense is not of the turf but of the cut piece of it, and the Celtic root may be connected to that of piece.