This brings to mind a very similar question I had wanted to ask.

What about 'bank' and 'banc'? The building is a bank, I do my financial business at the bank. My draft promissory notes (note the adroitness with which I elude the 'check/cheque' argument) say 'Ripoff Bank.' Yet the name of the corporation that owns and operates all the retail banks in the chain, and all of the other financial undertakings is 'The Ripoff Banc' or 'Ripoff Bancshares.' I assume this is coming from the French, but I'm unclear on what, exactly, are the apparently very clear differences.