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: habitational name from either of two places in Devon named Hunnacott, from either the Old English personal name Hunā or Old English hunig ‘honey’ + cot ‘cottage’. There is also a place named Huncoat in Lancashire, which has the same origin, but the distribution of the surname in England suggests that it probably did not contribute to the surname.