E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A flag with a blue ground and white square in the centre, hoisted as a signal that the ship is about to sail. Peter is a corruption of the
French partir (leave or notice of departure). The flag is hoisted to give notice to the town that any person having a money-claim may make it before the ship starts, and that all about to sail are to come on board.
According to Falconer, it is a corruption of the blue repeater.
In whist, it is a call for trumps; that is, laying on your partners card a higher one than is required.
To hoist the blue Peter. To leave.
When are you going to sail?
I cannot justly say. Our ships bound for America next voyage but Ive got to go to the Isle of Man first And I may have to hoist the blue Peter any day.Mrs. Gaskell: Mary Burton, chap. xiii.