wafer (n.)

late 14c., "thin cake of paste, generally disk-shaped," from Anglo-French wafre, Old North French waufre "honeycomb, wafer" (Old French gaufre "wafer, waffle"), probably from Frankish *wafel or another Germanic source (compare Flemish wafer, altered from Middle Dutch wafel "honeycomb;" see waffle (n.)). Eucharistic bread first so called 1550s.