nut up v. to become bold, courageous, or forthright; to sack up, man up. (source: Double-Tongued Dictionary)
Further reading
What’s it like to hike the Pacific Crest Trail all the way from Mexico to Canada? You’ll end up with sore muscles and blisters, and great stories to tell. Along the way, you’ll also pick up some slang, like NoBo, SoBo, Yo-yo and...
The slang phrase someone ate and left no crumbs means the person did something really well. In a previous call, a listener who works in theater noted the use of ate to mean “did something well,” as in they really ate that haircut! This...