lighter (n.1)
"barge," late 15c., agent noun from light (adj.1), with a sense of lightening a load, or else from Dutch lichter, from lichten "to lighten, unload," on the same notion. They are used in loading or unloading ships that cannot approach a wharf.
lighter (n.2)
"person who lights," 1550s, agent noun from light (v.2).