"Yeah verily" is a supposedly medieval English expression denoting the positive response to someones statement or expression made. It was popularized in the comedy movie: The Court Jester -
Danny Kay in the comedy movie: Court Jester, used the expression - "Yeah Verily ...". It was a positive, humorous emphasis pinned after a statement made, with the idea of: Yes that's true, yes in agreement with the previous speakers statement. It has nothing to do with the "cheap expression" suggested earlier.