Cash On The Barrelhead Meaning

(idiomatic) Money in the form of paper currency or coins, paid immediately at the time and place of a transaction.

Example: 1938 Sept. 1, Charles B. Parmer, "Serial Story: Photo Finish—Twelve," Telegraph-Herald (Iowa, US), p. 11 (retrieved 23 July 2013):
  "[W]e're selling , to the highest bidder, and for cash on the barrel head. . . . Cash in hand, no checks accepted."
1947 March 31, Foreign Relations: Potent Weapon, Time:
  [I]n 1946 the U.S. exported $2,166 million worth of food. . . . Most of this ($1,354 million) was paid for, cash on the barrelhead. But $628 million was the U.S. contribution to UNRRA stocks, and $184 million went through Lend-Lease.
2003 Feb. 25, Paul Krugman, "Threats, Promises and Lies," New York Times (retrieved 22 July 2013):
  In return for support of an Iraq invasion, Turkey wanted—and got—immediate aid, cash on the barrelhead, rather than mere assurances about future help.