Author Paula Kadose Radetzky (University of California, Berkeley) notes that although “Willy-Nilly” originally meant ‘unwillingly’, it has now evolved into meaning (almost) the reverse, viz. ‘howsoever one pleases’.
Raising the question:
“How does an expression go from meaning one thing to meaning another – even its opposite?” To find out, read : To Will or Not to Will: The Evolution of willy-nilly. The paper also hints at opportunities for future research, noting the author’s intent to investigate : Hodge-Podge, Dilly-Dally and Zig-Zag.
also see: Much ado ablaut flim flam