When my students are first working with the Grand Staff, they are often confused about the placement of the various clefs.
In piano music, we generally use only the G-clef (Treble clef – not “trouble clef” as some think!) and the F-clef (Bass clef) I try to show students how the curvy part of the G-clef wraps around the G above middle C and the F-clef looks sort of like an F marking the F below middle C. I draw out G and F on the staff to show how these could have looked.
Originally, instead of a special clef symbol, the reference line of the staff was simply labeled with the name of the note it was intended to bear: F and C and, more rarely, G. These were the most often-used ‘clefs’ in Gregorian chant notation. Gregorian chant developed mainly in western and central Europe during the 9th and 10th centuries, with later additions and redactions.
Over time the shapes of these letters became stylized, leading to their current versions.