From Old English (before 12th century), from Proto-Indo-European '*mori-' ("body of water, lake, sea"), from PIE *mori- ("body of water, sea").
A tract of open, uncultivated upland, typically covered with heather; a boggy, peaty wasteland.
From Old English 'mōr' (moor, morass, swamp, wasteland), from Proto-Germanic '*mōraz' (moor, swamp, sea), from PIE root *mori- (body of water, lake, sea). The original meaning was 'standing water' or 'swamp,' which shifted to describe the boggy uplands where water collects. The same PIE root produced Latin 'mare' (sea), giving us 'marine,' 'maritime,' and 'marsh.' The connection is that moors are