Methos tells Joe a story about gluttonous Romans using vomitoria to purge themselves after eating a heavy Roman meal. His usage of the word is a popular misconception. The Romans did not use a vomitorium to purge their meals when overeating.
The word 'vomitorium' does come from the Latin root 'vomere' meaning 'to vomit' or 'to spew forth'. But it does not refer to the contents of one's stomach. It is a popular myth is that they went to the vomitorium to vomit.
Vomitoria actually refers to the passages or corridors through which spectators could "spew forth" into their seats at public entertainment venues. In Rome, the Coliseum (the largest amphitheatre ever built), had 76 vomitoria for the common spectators to enter or leave. There were another four vomitoria for the exclusive use of the Imperial family. As a result of having these 80 spacious entrances or exits, 50,000 people could get in or out of the Coliseum within 15 minutes. Vomitorium/vomitoria are still used today by archaeologists as architectural terms. Vomitorium is one of Latin's most misused word.