wil·ly-nil·ly 
(wĭl′ē-nĭlē)
(wĭl′ē-nĭlē)adv.
1. Whether desired or not: After her boss fell sick, she willy-nilly found herself directing the project.
2. Without order or plan; haphazardly: “We laid our sleeping bags out willy-nilly, as if having fallen from the stars” (Rick Bass).
adj.
1. Being or occurring whether desired or not: willy-nilly cooperation.
2. Disordered; haphazard: willy-nilly zoning laws.
[Alteration of will ye (or he or I), nill ye (or he or I), be you (or he or I) willing, be you (or he or I) unwilling.]