Man, I don't even know what a 'Bowzer' is either.
I'm sleeping on my vocabularium expansion.
water tanker - equates to -
river imp
(In my mind, I equate a 'bowser' to a bruising, hulk sort of character. A 'kuppa', or as I more familiarly recognize it as, a KAPPA, is a river monster/spirit. Forgot to mention a Japanese spirit. On the other hand, I equate a 'koopa' to the green-shelled antagonists to Sir Mario, but the way they sport beaks and shells, well, that is a direct tie-in to the legend and mythos associated towards the demonic, foul-tempered KAPPAs.)