If I were the lawyers at ING, I would be sending Google it cease-and-desist with regards to selling any domains with banking related terms. I actually think they would have a reasonably strong claim.
To be honest both cases are equally strong. Trademark by a bank, and English gerundial suffix. I want to see their lawyers knife fight in a ring while burning piles of cash, it would be an entertaining self resolving problem!
And grammar teachers would sue ING?
On what grounds? ING can sue on grounds of owning a trademark.