What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
Originally: a fragrant oil obtained from orris root (Iris germanica and other species). Later: each of three isomeric cyclic ketones ("α-irone", "β-irone", and "γ-irone") found in this oil and in other plants such as violets, and used in perfumery.
Late 19th century; earliest use found in Bulletin Pharmacy. From German Iron, with remodelling of the ending after -one.