Cadillac-sur-Garonne was founded in 1280 to serve as a river port for the castle of Benauges by the lord of the castle, Jean I de Grailly.
Name
Cadillac-sur-Garonne is attested in the form Cadilacum in 1306. Toponymist Ernest Nègre explains the name as made up of personal Roman name -Catilius, with the suffix -acum.
The suffix -acum is of Gauloise origins (in the form -acon). It served to localise persons or the origins of persons before it became to demark the property of some person.