From "The Winning Way", by Don Scott, page 244.

During the war, American servicemen on leave in Sydney had a reputation for backing 100/1 & 200/1 chances regardless of form. Bookmakers competed for their custom & regarded their bets as "fruit for the sideboard". Retired rails bookie Aub Guyatt tells the story of one figures bookie who decided to gamble to get his fruit.

The bookie was only a small operator, laying each horse to take out $300 (pounds) and no more. provided he laid all the horses for the same amount and made a perfect book, he stood to win 20 per race or 140-150 per meeting. This particular day at Randwick he had worked hard and well at his trade & had made a profit of 150 on turnover on the first 6 races. Flushed with success, he put up his prices for the last with the worst horse, Mayflower, at 100/1. An American sailor walked up with a $10 note.
"Ten pounds on Mayflower, please".
"Not that much," said the bookie, remembering his perfect book, "I'll lay you 300 to 3".
"Come on", said the sailor, "it's only 10 pounds".
"All right", said the bookie, deciding fo once in his life to gamble & grab some fruit for the sideboard. "You can have 1000 to 10.

Mayflower won the last by a head. The Ameican came back flourishing his ticket. The bookie, forced to borrow from others to settle & swearing under his breath neve to gamble again, started paying out the 1010 pounds.

"Whatever made you back Mayflower"?, he asked.
"My ancestors came over to America on the Mayflower", said the sailor.
The bookie went on counting out the money. "I wish they'd come over on the ************ Titanic", he said.


This may not be the origin of the saying, but it's a funny story connected with it.