Chamor Nosai Seforim

On The Main Line writes that the term חמור נושא ספרים, may have a Koranic origin.

The first Jewish source he find for it is in the sefer Chovos Halvavos.

I view it as a emotional issue rather than a real problem. It might not feel right but I don't see anything wrong with it.

Besides, as he writes, its quite possible it entered the common lexicon by the time he wrote it.