From Old English (before 12th century), from Proto-Indo-European '*kaito-' ("forest, open land"), from PIE *kaito- ("forest, open land").
An area of open uncultivated land, especially in Britain, with characteristic vegetation of heather, gorse, and coarse grasses.
From Old English 'hǣþ' (heath, wasteland, open ground), from Proto-Germanic '*haiþī' (wasteland, open land, heath), from PIE root *kaito- (forest, open land). The same root gives us 'heathen' — literally a 'person of the heath,' a dweller in the uncultivated countryside. When Christianity spread through Germanic lands, it reached
'Heathen' literally means 'person of the heath.' Christianity spread through Roman roads and towns, so rural heath-dwellers were the last pagans — their landscape became their religious label. London's Heathrow Airport sits on what was literally a 'heath row' — a row of houses on the edge of Hounslow Heath.