facetious /fəˈsiːʃəs 
/ ▸ adjective treating serious issues with deliberately inappropriate humour; flippant: a facetious remark.
– DERIVATIVES facetiously /fəˈsiːʃəsli / adverb facetiousness /fəˈsiːʃəsnəs / noun – ORIGIN mid 16th century (in facetiousness in the general sense ‘wittiness’): from French facétieux, from facétie, from Latin facetia ‘jest’, from facetus ‘witty’.
EnglishOxford Dictionary of English
