What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
1Chiefly Pharmacology. The compound hexamethylenetetramine, (CH₂)₆N₄, or a derivative of this (often with mandelic acid), especially when used as a urinary antiseptic.
2Pathology. In full "methenamine silver". A solution of methenamine and silver nitrate, used in several histological stains.
1920s; earliest use found in Pharmacopeia United States. From methene + amine.