What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
A testicle from a monkey or ape used as a possible means of rejuvenation, either by being grafted on to a man, or by the injection of an extract. Frequently in plural Also attributive (allusively).
Early 20th century; earliest use found in The Sheboygan Press. From monkey + gland.