"I'd like you to lend me some money"
Etymology is from the cartoon "Popeye", where the character Wimpy would frequently utter this phrase. He was a glutton, and would consume burgers at a ferocious rate but could rarely pay for his habit.
The phrase implies the underlying feeling that the person will unlikely actually pay for the hamburger (or whatever) on Tuesday (or ever, for that matter.
I told my bank that I'd gladly 'pay them tuesday for a hamburger today' to buy that new sportscar, but they wouldn't approve me.