Many people claim that undershirts have moisture-wicking properties, and while its true that your undershirt wicks away some of the sweat, the reality is it simply provides a barrier between your underarm and your dress shirt fabric
[20] These 17951820 fashions were quite different from the styles prevalent during most of the 18th century and the rest of the 19th century when women's clothes were generally tight against the torso from the natural waist upwards, and heavily full-skirted below (often inflated by means of hoop skirts, crinolines, panniers, bustles, etc.)
I also find that the more mass brands/high street brands CAN run more generous and they (thankfully) offer solutions for a broader body types (often I go down to M or even a S if super oversized and I want a more tailored fit)
Or add another mix-in, like cubes of sharp cheddar cheese or green onions instead of red onions
it's provenance unconfirmed after an exhaustive search