Humans should get "All healing received is maximized (ie: treat it as if the dice each rolled their maximum value)" to reflect how humans weirdly bounce back from things that should have been fatal.
It's an initialism. Aitch-Eff-Why. I've never heard it pronounced before.
Humanity: Fuck Yeah!
Subgenre of science fiction subverting the "humans are average" trope by celebrating the things that make humanity unique among hypothetical alien civilizations. Lots of emphasis on our durability, endurance, creativity, and potential for overwhelming violence.
I have a homebrew that I need to revisit and fix the formatting of for mixed heritage PCs, and the system I came up with meant that I had to give every race four traits. Some of these would be minor, like darkvision, but there had to be four. I went with a once-per-day refuse-to-die ability and a proficiency-per-day advantage on a roll of your choice, so that the one thing humans do best is push through the tough situations