In ancient Greek society, there was a strong emphasis on moderation, self-control, and restraint. Public behaviors that were considered excessive or disruptive, such as burping or flatulence, may have been frowned upon or considered失礼な. This is because these actions would have been seen as a lack of self-discipline and could have disrupted social interactions.
Additionally, the ancient Greeks placed great importance on hygiene and cleanliness. Public behaviors that were considered unhygienic, such as burping, may have been seen as offensive.