know from nothing

not know from nothing

To be completely ignorant or uninformed (about something). Don't ever second-guess my judgment again, you hear me? You don't know from nothing! Don't mind her, Phil. She doesn't know from nothing.
See also: know, not, nothing
Farlex Dictionary of Idioms.

know (or not know) from nothing

be totally ignorant, either generally or concerning something in particular. North American informal
See also: know, nothing
Farlex Partner Idioms Dictionary
See also:
  • doesn't know beans
  • come it
  • come it (with one)
  • all in (one's) head
  • (I) don't mind if I do
  • don't get me wrong
  • a sob story
  • don't bet on it
  • don't give up the ship
  • don't beat a dead horse