nut up

verb2

1. •
   (slang) To show courage and hide one's apprehension.
2. •
   (slang) To lose one's temper, go nuts.

   • And what if some shit went wrong? Pimp was known to get crazy over minor shit. I didn't know if I could trust him to pull off a job like this without nutting up in the middle of the mix. — 2006