Most sedatives can also promote sleep. Overdosage of a sedative medication can lead to dangerous respiratory depression (slowed breathing). A large group of medications with sedative effects are the benzodiazepines.
The first tranquilliser librium (chlordiazepoxidehydrochloride) was developed by the Hoffman-la Roche in 1958. The word tranquillise entered the english language much earlier (1623), and was derived from the latin tranquillus via the french tranquille meaning calm.