What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
Originally: a supposed hydrocarbon having the formula C₆H₄. Now: each of three divalent radicals —C₆H₄—, derived from benzene by the loss of two hydrogen atoms. Usually attributive or in the names of chemical compounds.
Mid 19th century. From phenyl + -ene.