Phonetic spelling: Naht-noh co kgi-yuck-ja-doe moh-run-dah.
Transliteration: Put down a knife the first letter you won’t know
Full Translation: Even if there was a Korean machete next to you you wouldn’t recognize that letter
This is another one of those things that you pick up on because of the nature of “friendly” conversation amongst friends in Korean culture.
She learned it from her college friends who loved to show affection by picking on each other
What happens is a traditional Korean machete is shaped like the first letter of the Korean alphabet, ㄱ. The point of the joke is that the person this is being said to is so dumb that they wouldn’t recognize the first letter of their alphabet even if it was laid right in front of their eyes.
Context of performance: I was just asking if she knew any interesting Korean everyday phrases.
I think it’s interesting because in English there’s a similar phrase, I believe which is said to someone who’s saying something slightly dumb. We’d say something along the lines of “You’re so dumb you wouldn’t see it even if it was right in front of your eyes”. I also find this one interesting because it plays along to the playful banter culture of Korean friends where insulting each other is the way to show affection.