lozenge (n.)
figure having four equal sides and two acute and two obtuse angles, early 14c., from Old French losenge "windowpane, small square cake," etc., used for many flat quadrilateral things (Modern French losange). It has cognates in Spanish losanje, Catalan llosange, Italian lozanga. Probably from a pre-Roman Celtic language, perhaps Iberian *lausa or Gaulish *lausa "flat stone" (compare Provençal lausa, Spanish losa, Catalan llosa, Portuguese lousa "slab, tombstone"), from a pre-Celtic language.

Originally in English a term in heraldry; meaning "small cake or tablet (originally diamond-shaped) of medicine and sugar, etc., meant to be held in the mouth and dissolved" is from 1520s.