'barbital' originates from chemical nomenclature based on 'barbituric (acid)' (coined in the 19th century in Modern Latin/European chemistry), specifically from the word 'barbituric' used to name the acid from which derivatives were made.

'barbituric (acid)' was named in 19th-century chemical literature; derivatives of that acid were named by adding typical chemical/vernacular endings, yielding 'barbital' for the specific derivative, and the plural form 'barbitals' followed as a simple plural.

Initially the root referred to the chemical 'barbituric acid' and its derivatives as a class; over time 'barbital' came to name a particular drug and 'barbitals' came to be used for that drug or for barbiturate drugs generally.