knees-up

UK 20th century. From the song "Knees Up Mother Brown" (from at least 1918; published 1938). Suggesting the motions of dancing.

knees-up (plural knees-ups)

1. (British, informal) A party.
   • 1956, Wolf Mankowitz, My Old Man's a Dustman:

     Let's have a bit of a knees-up, Arp.

   • 2017 November 24, Jacob Steinberg, “There’s no pleasing some people”, in The Guardian‎^[1]:

     However, having heard all the mutinous chants Taxpayer FC’s fans sang about Gollivan at Vicarage Road, Moyes has realised it’s probably part of his remit to spread some love and urge everyone in east London to have a good old Cockney knees-up before Friday’s visit from Leicester City.

   • 2017 December 1, Mary McCool, “Prince Harry set to spend his stag do in Scotland as bookies slash odds – but Vancouver, Barcelona and Berlin are also in the running”, in The Scottish Sun‎^[2]:

     William Hill today cut the price of a Scottish knees-up from an original 25/1 into 9/1 favourite.