"to fasten (a ship) in a particular location by or as by cables, anchors, etc.," late 15c., probably related to Old English mærels "mooring rope," via unrecorded *mærian "to moor," or possibly borrowed from Middle Low German moren or Middle Dutch maren "to moor," from West Germanic *mairojan. Related: Moored, mooring. French amarrer is from Dutch.
"tract of open, untilled, more or less elevated ground, often overrun with heath," c. 1200, from Old English mor "morass, swamp," from Proto-Germanic *mora- (source also of Old Saxon, Middle Dutch, Dutch meer "swamp," Old High German muor "swamp," also "sea," German Moor "moor," Old Norse mörr "moorland," marr "sea"), perhaps related to mere (n.1), or from root *mer- "to die," hence "dead land."
The basic sense in place names is 'marsh', a kind of low-lying wetland possibly regarded as less fertile than mersc 'marsh.' The development of the senses 'dry heathland, barren upland' is not fully accounted for but may be due to the idea of infertility. [Cambridge Dictionary of English Place-Names]
Hence moor-fowl "grouse" (c. 1500); moor-hen (mid-14c.); moor-cock (c. 1200 as a surname).
"North African, Berber, one of the race dwelling in Barbary," late 14c., from Old French More, from Medieval Latin Morus, from Latin Maurus "inhabitant of Mauretania" (Roman northwest Africa, a region now corresponding to northern Algeria and Morocco), from Greek Mauros, perhaps a native name, or else cognate with mauros "black" (but this adjective only appears in late Greek and may as well be from the people's name as the reverse).
Also applied to the Arabic conquerors of Spain. Being a dark people in relation to Europeans, their name in the Middle Ages was a synonym for "Negro;" later (16c.-17c.); being the nearest Muslims to Western Europe, it was used indiscriminately of Muslims (Persians, Arabs, etc.) but especially those in India. Cognate with Dutch Moor, German Mohr, Danish Maurer, Spanish Moro, Italian Moro. Related: Mooress.