What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
Any of a group of flattened elliptical flagellates, formerly regarded as protozoans by zoologists or as green algae by botanists, and typically characterized by chloroplasts and two flagella.
Mid 19th century; earliest use found in Andrew Pritchard (1804–1882), microscopist. From crypto- + monad.