lagg

Most likely from Swedish lagg (“moist, marshy area around a bog”), though compare the dialectal (Sussex, Somerset) English term(s) lag ("long, narrow, marshy meadow, usually by the side of a stream") and leg ("long, narrow meadow, gen. one which runs out of a larger piece of land"), apparently from leg (“limb”) (as of a body, or body of water). (Compare also Middle English lech(e) (“sluggish stream flowing through bog; bog”), usually attested with ch (whence English letch), but infrequently found as leg, lage in names.)

来源：wiktionary