I've happened to hear "willy-nilly" used for the third or fourth time this week to mean "every which way" or "haphazardly."

I was given to note while listening to an interview with James Randi, of all people, that this seems to be one of those meanings that simply caught on after a misuse. Oxford resultingly lists it, but its original meaning remains "whether one likes it or not," as in "you're coming with us, willy-nilly."

It sounds odd if you're unaccustomed, but is more intuitive in light of their etymology note:

early 17th century: later spelling of will I, nill I ‘I am willing, I am unwilling’.