English: habitational name, most probably from a place in Dorset, named from Old English h?l ‘omen’ + well(a) ‘spring’, ‘stream’; the reference is presumably to pagan river worship. Two minor places with this name in Devon are probably named as ‘elder-tree spring’, from Old English ellern ‘elder tree’ + well(a). The surname is now found chiefly in the West Midlands. Compare Halliwell.
Dictionary of American Family Names, Oxford University Press, ISBN 0-19-508137-4