Sad Clock Why Did W.H. Auden Title Sad Poems With Flippant Titles?

Why did W.H. Auden title sad poems with flippant titles? - sad clock

I read Auden Stop all the Clocks "sad poem for a loved one dies. But it is also has the right, not easy, "Funeral Blues". He used to appoint one of his poems entitled unhappy with a light heart. I was wondering if anyone knew why it has done?
Thanks in advance