When Aguirre told the poor sap on the other end of the phone, "Not on your fucking life", he was invoking Caesar Augustus's phrase "ad Kalendas Graecas".
Note: The phrase means "never" and is similar to phrases like "when pigs fly". The Kalends (also written Calends) were specific days of the Roman calendar, not of the Greek, and so the "Greek Kalends" would never occur.
--Wiki