Marlon is an English male given name of unknown meaning. It may have originated as a variant spelling of Marland, an English surname derived from a place name meaning “land by lake” or “land by the sea” from English elements mere (lake, pool; sea, ocean) via a PIE root word; and land (land) also derived from a PIE root word. It could also be derived from Moreland, another topographical English surname meaning “land by the marsh” or “land by the fen”. It’s also possible that Marlin is related to French merlan meaning “whiting (fish)”, perhaps an occupational name for someone who sold that particular type of fish.
Marlon may also have been derived as a variant spelling of Merlin derived from Welsh Myrddin meaning “sea fortress”.