Green’s Dictionary of Slang

incomprehending, resigned, weary.

1933		S. Walker Night Club Era 182: The Inspector, whose best friends never accused him of being a mental giant, went through this puzzling period with a hurt, what-the-hell? expression on his Irish face.
1947		B. Stiles Serenade to the Big Bird 60: She had a sort of what-the-hell look on her face.
1958		L. Block ‘Murder Is My Business’ in One Night Stands (2008) 117: And they [i.e. prostitutes] walk with a what–the–hell shuffle.