Halbwelt Kultur is a German portmanteau meaning 'Underworld Culture' and comes from a 1927 book Ladies of the Underworld by Netley Lucas: .
The German is gross in his immorality, he likes his Halb-Welt or underworld pleasures to be devoid of any Kultur or refinement, he enjoys obscenity in a form which even the Parisian would not tolerate.