Word Origin & History
placard1481, "formal document authenticated by an affixed seal," from M.Fr. placquard "official document with a large, flat seal," also "plate of armor," from O.Fr. plaquier "to piece together, stick, plaster," from M.Du. placken "to patch" (a garment), "to plaster," related to placke "patch, stain." Meaning
"poster" first recorded 1560, though this sense is in M.Fr. from 15c.