What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
Definition of Unio bed in US English:
Unio bed
noun
A layer of rock rich in fossilized shells of freshwater mussels; specifically that in the lower part of the upper strata of the Purbeck beds in Dorset;.
Origin
Mid 19th century; earliest use found in Quarterly Journal of the Geological Society of London.
