Probably from a Celtic word meaning 'piece/portion,' for the uniform blocks in which peat was cut.
Partially decomposed organic matter formed in waterlogged conditions, cut and dried as fuel or used as a soil amendment.
From Anglo-Latin 'peta' (a piece of peat), possibly from a Celtic source akin to Cornish 'peyth' or Welsh 'peth' (thing, portion). Peat was dug in uniform blocks or 'portions,' and the name may simply mean 'a cut piece.' Key roots: *pett- (Celtic: "piece, portion, thing").