We need a precise definition of an ezelsbruggetje--even an etymological breakdown.

I'll add this. Kluge (a Germanic philologist whose etymological dictionary of New High German is both popular and good) considers that German Esel is perhaps one of the earliest loanwords out of Latin. From Vulgar Latin asilus, it is represented in Dutch ezel, Old English e(o)sol, and Gothic asilus.

Dutch ezelbruggetje breaks down as ezel 'ass' + bruggetje 'little bridge' (< brug 'bridge' + -etje diminutive suffix).

Note: when I said I understood the change in meaning in the term pons asinorum, I did not mean I agreed with it. I've been a fan of the ars memorativa since first reading Frances Yate's book about it as a college freshman.