Transferred use of the mainly Scottish surname, in origin a local name for someone who came ‘from the island’ (Anglo-Norman de l'isle). (The island in question would in many cases have been an area of higher, dry ground in a marsh or fen, rather than in a sea or river.) There may have been some confusion with Lyall.
English: 1. habitational name from a place in Gloucestershire, which is probably named from Old English ellern ‘elder tree’ + wudu ‘wood’. 2. from the Old English personal name Ælfweald, composed of the elements ælf ‘elf’ + weald ‘rule’. In the British Isles this spelling is now found predominantly in northern Ireland.