An Etymological Dictionary of the German Language/Annotated/Pennal
Pennal, neuter ‘pen-case,’ Modern High German only, formed from Middle Latin pennale; with this compare Pennal meaning, ‘grammar-school, high-school, pupil.’ To the students at the university the school might seem as a huge array of pen-cases, and “in jest the freshman too was called a ‘pen-case,’ probably because he attended lectures regularly, and so carried his pen-case with him.”