What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
Originally: †facial or physical characteristics taken as indicative of character, personality, etc. (obsolete). Later: the art or practice of judging character from facial or physical characteristics.
Early 18th century; earliest use found in John Harris (c1666–1719), writer and lecturer on science. From physiognomic: see -ic.