From what language does the phrase non sequitur originate, and does it mean?

The phrase was borrowed into English in the 1500s by people who made a formal study of logic. For them it meant a conclusion that does not follow from the statements that lead to it. But we now use non sequitur for any kind of statement that seems to come out of the blue

"a" because he is appealing to logic as oppose to appealing to the audience's emotions.