What does "louver" mean?

Louver: A small lantern. See Lantern, 2 (a) [Written also lover, loover, lovery, and luffer.] Louver boards or boarding, the sloping boards set to shed rainwater outward in openings which are to be left otherwise unfilled; as belfry windows, the openings of a louver, etc. -- Louver work, slatted work.