early 15c., "thin layer of skin or soft tissue of the body," a term in anatomy, from Latin membrana "a skin, membrane; parchment (skin prepared for writing)," from membrum "limb, member of the body" (see member). The etymological sense is "that which covers the members of the body."
"having a membrane; of or like a membrane," 1590s, from French membraneux (16c.), from membrane, from Latin membrana "a skin, parchment" (see membrane). The alternative form membraneous is recorded from 1630s.
"outer membrane of the fetus," 1540s, medical Latin, from Greek khorion "membrane enclosing the fetus, afterbirth," from PIE root *ghere- "gut, entrail." Related: Chorionic.
"mucous membrane of the inner surface of the eyelids," 1540s, medical Latin, short for membrana conjunctiva "conjunctive membrane" (see conjunctive). So called because it conjoins the lids and the globe of the eye. Related: Conjunctival.