Combination of "H.A.M." and "City".
"H.A.M." is an acronym that stands for Hard as a MoFo.
"City" is used to emphasize the amount of something.
H.A.M. City basically means putting ones full potential into something. Or something that's extremely abundant.
Jeff- "I went HAM City at the gym"
Patrick- "Funny because my mom and I just went HAM City with the Popeyes chicken"
Jeff- "Seriously man -_-"
City ham is a term used in some parts of the United States for any bougie, silly man, lightly cured of distasteful behavior, which must be kept at a distance to preserve it. It is generally used to get "wet cured", that is injected with or soaked in a brine solution containing high concentrations of salts.
"So, Jamie, which one of your side meats was that? Was he the sausage you were bragging about the other day?"
"No, just a City Ham, but he still makes for a decent snack."