NONCHALANT

ITS a lovely word isnt it? its french i beleive,sadly us brits rarely use it,like say im walking down the street, and i bump into somebody i know and the convo goes
them.hiya how are you?
me,yeh im good in fact im feeling very nonchalant
them,what?
me,y know im nonchalant man
them,walk off scratching their head
i wonder if the french greet each other like that?
another french term i like is lassez fair
suits me that.
p.s quick music quiz, which is the only british chart hit that as the word nonchalant in the lyrics?