Most of these were straight variations on "Yes", with the exception of "In flagrante delicto" (Kathryn) and Iä, Iä (the Shoggoth).

The exceptions are "Yes, Master" (straight minion), "Amen, Brother!" (overenthusiastic Pentecostal/Charasmatic Church) and "Yea, verily".

Now, I thought that I picked up "Yea, verily" from "Guards, Guards" by Terry Pratchett - a novel with a particularly useless set of cultists.

However, thinking about it, I may also have picked it up from an old Danny Kaye film (The Court Jester), where he is being given an accelerated knighthood, and the refrain from the ceremony is "Yea verily, verily, yea", chanted faster and faster as the people in charge realise that they are running out of time.

The film is slightly more memorable for the "Flagon with the Dragon" dialogue.