Explanation: Posidonius was a Greek writer of the 2nd-1st century BCE who made note of numerous Celtic customs of the period - with no attempt to hide his own judgement of their culture. Notable is that the Celtic Gauls sat to eat, instead of reclining at meals, like civilized Mediterranean peoples did! How absolutely BARBAROUS!

When I recline to eat, I get the heartburn. I’m barbarous in other ways as well.