verb/a.vwaʁ lə ka.faʁ/
to have the blues, to feel blue
“Il fait du soleil aujourd'hui, mais j'ai le cafard.” — It's sunny today, but I feel blue.
From cafard (“melancholy”). This term originated from poetry writer Baudelaire in “Les Fleurs du mal” in 1857. Le cafard came to mean an extreme depression or sense of pointlessness.