Should you, after reading the title, now be questioning your basic grasp of Japanese, goal achieved. But seriously, I’m not kidding. Didn’t you ever wonder about this word, after having looked up the kanji used to write nigate, which only means unskilled nowadays, and finding that niga(i) is the word for bitter? I sure did.
The truth is, the original usage of this word was perfectly understandable. But let’s make this another episode of let’s read Japanese dictionary and consult the equivalent of the Bible for the linguist/ambitious student:
To summarize, as the heading of this post already states, a bitter poisonous substance was somehow thought to be connected with unusual powers. And one thing we learn about reading classic dictionaries is that we can ignore the examples. They’re mostly from ancient Japanese and are hardly understandable, and they don’t reflect current usage. Use a good dictionary such as 明鏡国語辞典 for that.
I suppose now would be the time for me to tell how we get a 180° flip in meaning to arrive from “super skill” at “no skill”, but alas, I’ve got no idea and I didn’t find anything on the net. Well, I could certainly speculate and make up my own theory, but I’d rather not to that without any evidence to back it up; and it may lead some people to think of me an authority and lead them to take my hypothesis for a fact. Not what I want.
With that being said, I’d love to hear you personal theory in the comments, feel free to speculate.