BBQ Gun
From the best I can tell the term came out of the Law Enforcement Family of South East Texas. The gun you carry day to day will show some wear and tear and dings and knocks. Now, when you go to a party, usually in those parts a 'Bar Bee Que', you put on a nicer gun, something with maybe a little engraving, and nice finish and some grips that draw attention. When I moved to San Antonio about 23 years ago they weren't familiar with the term, they are now. Anyway, after the BBQ, the nice looking gun goes back in the case and the working gun comes back out.