My informant is my grandmother, who is quite a devout Catholic and has lived in the deserts of Phoenix most of her life. During one of my visits home this year we went to a baseball game together. We were sitting in the sun and I heard her exclaim on of her favorite phrases, “good Lord, I’m sweating like a sinner in church.”.
Me: “What do you mean when you say that?”
DC: “It means that it’s really, really hot out and you’re sweating quite a bit. Like a sinner, sitting in the presence of God would feel nervous and sweat I suppose. It’s not meant to be super serious, just a funny thing to say when you are sweating a lot and you might be embarrassed about it.”
Me: “Do you remember where you heard it first or learned it from?”
DC: “No, I can’t say I do. I may have picked it up from my mother, but I’m not quite sure. I’ve always just kinda said it . . . I don’t think your grandpa ever said it or any of siblings for that matter . . . so maybe I picked it up from a friend along the way? I don’t know really.”
This phrase most likely means that a person is sweating like one would imagine someone who has sinned would sweat if they were sitting in church and haven’t repented. Like, they are lying to God and are sweating in nervousness because they suppose God knows, but they are there anyway. It comes from my grandmother who is a devout Catholic, so in using this phrase she is performing her Catholic identity to those around her who are also presumably Catholic or Christian and would understand what she meant by a sinner sitting in church. We also live in quite a warm climate, where any time spent outside between the months of March and October results in sweating, so sweat being the object of a simile makes sense in that it is a common experience felt by everyone around them. It is meant to be comic and making light of the situation because the person exclaiming it, is most likely uncomfortable and is calling attention to the situation in a comic way perhaps in order to alleviate their embarrassment of sweating so much in public.