Decetia is an old place name in the Loire region of ancient Celtica. The name is interesting because of the possibility that it is a dialectical variant of decant- ‘hundred’. So compare the northern British tribe Decantae and the southern French term frequent in inscriptions dekanton. The form is comparable to the Alpine town named Brigetia, more obviously a variant of ‘Brigantia’. So Decetia may perhaps memorialise a little people speaking a little language in the heart of Gaul.
The term dekanton is likely due to the Volcae, a Galatian group originating in central Europe who probably entered southern France c. 250 BCE, around the time the Galatai were attacking eastern Europe, Greece and Turkey.