What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
A gland present in the inner angle of the eye in those birds, mammals, and other vertebrates that have a nictitating membrane or ‘third eyelid’, typically secreting a slightly oily lubricant.
Early 19th century; earliest use found in John Fleming (1785–1857), naturalist and Free Church of Scotland minister.