Steve, here is one place I found "grodie". Yes, I am fairly sure it is an Americanization. Perhaps it should be noted that we pronounce it with a long O as found in it's root word. "Grotty" would appear to have a short O. Does it?

Begin rant
Almost daily, the conscientious people who work in the field of graphics (a term that has come to include printers, illustrators and graphic designers,) are forced to deal with the fallout of varying degrees of illiteracy, poor grammar and misusage of words. They are torn by the dilemna of whether to simply produce products bearing the glaring errors as they were submitted, (WYSIWYG,) or to take the time and the responsibility to correct the mistakes, thus delaying production and increasing costs. The problem is often so bad that the graphics people actually lose money because of the amount of time needed to correct such errors. A printer, for instance, should only be responsible for printing what is submitted. However, if the finished product is filled with errors, often the clients won't pay - even though the mistakes are theirs!

This issue, I know, is something of a spin-off from the original topic. However, I have been confronted with this problem over and over - as have most others who have worked in the graphics field. It shows to us how prevalent poor spelling, poor usage, etc., are and that there seems to be little distinction as to the level of education of the people who demonstrate such poor command of the language.
End rant