Australia, 1909—(horseracing) a bet is sure to pay off; (in extended use) something is a very strong probability—from the notion that the punter is so confident of winning the bet that he is prepared to put the whole city of London on a horse to win a brick, i.e., a ten-pound note
USA, 1923—in motorsports: to win a race—refers to ‘checkered flag’, denoting a flag with a black-and-white checkered pattern, displayed to drivers at the end of a race
UK, 1808—to make one’s beliefs or intentions plain—from the former practice of nailing an ensign to the mast of a ship, after damage during battle resulted in the ship’s colours no longer being clearly displayed, which otherwise might have been interpreted as a signal of surrender
a representation of the letter A in scarlet cloth which Hester Prynne is condemned to wear in The Scarlet Letter (1850), by Nathaniel Hawthorne—soon came to be used figuratively in the sense of a stigma, a mark of infamy
USA, 1887—of a child: to go to bed—‘Lilywhite’ refers to the whiteness of the bedsheets—from ‘lily-white’, meaning ‘white as a lily’, hence ‘of a pure white’
UK, mid-1950s—to set a course of exciting or dramatic events in motion—refers to firework instructions such as ‘light the blue touchpaper and retire immediately’