https://faroutmagazine.co.uk/leonard-co ... ight-cure/
Ahead of his residency at London’s Wembley Arena in 2012, his backing singers, The Webb Sisters, spoke with The Independent. They offered a vivid insight into what went on before their performances on his comeback tour. The duo revealed: “Leonard always asks us to be there half an hour before the show, so we can be there together as a band. It’s a great way of everyone sticking together,” they explain.
“There’s a whole array of beverages and we often have a whisky. Leonard loves a whisky. He used to have to drink three bottles of wine before going on stage because of nerves. Now it’s just a whisky.”
After he had guzzled his whisky, Cohen’s final ritual was beautifully absurd as he emphatically led his band through a Latin song. “It’s in Latin: ‘Pauper sum ego, nihil habeo’ – ‘I am poor, I have nothing’,” the sisters recalled. “It comes from Leonard. The bass player plays a note, Leonard starts singing and we all follow. The 10 of us then walk to the stage singing it. It’s a great focusing ritual. It’s a way of reducing the weight of what we feel. It’s really unifying.”
I thought I'd add a bit to the above info. There is an incident of a similar situation at Glastonbury 2008 as reported by Sylvie Simmons. Also, LC has been singing in Latin this chant-in-the-round since at least the 1970's. Here's an example with a video put up by Tom years ago from the film The Song of Leonard Cohen by Harry Rasky (1980) - https://www.youtube.com/watch?v=uFOjTVCPBjY
You can almost see the words they were singing written on a piece of paper.
There are slightly different translations, here's one -
ego sum pauper (I am poor)
nihil habeo (I have nothing)
me ipsum dabo (I will give my own self)