May
17
2010
能天気
のうてんき [nou tenki] – “Ability” (能) + “Weather” (天気) = being carefree, or a person who is carefree (perhaps recklessly so).
No one seems to have a good explanation for why this combination of characters came to mean what it does, but this casual term has been found in Edo period writings, so it’s quite old.
It can be alternatively rendered as 脳天気, 能転気, のーてんき and more recently ノー天気, but they’re all the same meaning.