Beer Gardens

Now I haven't heard that term in a long time. I remember when I was 10 I would spend two weeks with my Grandparents in Homestead, PA (near Pittsburgh). My Grandpap worked at the mill. My Grandma would send me down to the "beer garden" to fetch my Grandpap after work to come home for dinner. It was such a pleasant memory. When I would walk in he would grab me and sit me at the bar while he finished his boiler-maker. I would have an Orange Crush and a small bag of potato chips. I was sworn not to tell less it ruined my dinner. All the mill Hunkys would poke me and rub my hair and offer me some Iron City Beer. Of course, my Grandpap never let me have any. My Dad let me taste beer and I couldn't stand it. I spit it out. He thought it was funny. So when I'm at the bar now and I ask for a boiler-maker and the bartender has no clue, I have to show them how to do it. My question is, does anyone know why they call it a "boiler-maker". It is made by taking a shot glass of whiskey and dropping it in to a mug of beer. I'm just wondering.