in·sou·ci·ance
noun/ɪnˈsuːsiəns/
/ɪnˈsuːsiəns/
[uncountable] (formal)- the state of not being worried about anything
无忧无虑；漫不经心 - She hid her worries behind an air of insouciance.
她掩饰着自己的烦恼，表现得无忧无虑。
Word Originlate 18th cent.: French, from insouciant, from in- ‘not’ + souciant ‘worrying’ (present participle of soucier). - She hid her worries behind an air of insouciance.