In the Mishnah Pesachim 10:4, we are first taught of the obligation to ask the Ma Nishtana question/s at the Pesach Seder. This consists of an opening question:
?מה נשתנה הלילה הזה מכל הלילות/How is this night different than all other nights?
This is followed by four specific differences between tonight and all other nights. In some versions of the text, there are only three elements of the questioning. The Rambam codifies a list of five questions, yet points out that today we only say four of them.
There is discussion whether this is really three/four/five questions at all, or really one question with numerous elements in which the reader is identifying how tonight is different (detailed treatment here). This is not the point of discussion at hand (although the question is more pressing if we choose to understand the text as being one question), See here for insight on where we find answers to the question/s.
In modern times, the Ma Nishtana text of the Pesach Seder is commonly referred to as the Four Questions. When did this name originate? What is the earliest authoritative source we find using this title for the text?