The flag, serving as a signal of recall for departure, was used by the British Navy from 1777, and the name “blue peter” had become common by the end of the 18th century. An all-blue flag had earlier seen use for the same purpose by the Dutch East India Company. While “blue” obviously refers to the dominant colour of the flag, the origin of the second part of the term, “peter”, is unknown. Often said to be a corruption of “blue repeater”, there is actually no signal flag that goes by that designation. The use of the flag to spell the letter “P” dates from 1857 and so cannot have played a role in the origin of the term.
- (nautical) A blue signal flag with a white rectangle in the centre, signifying "P". When flown alone, indicates that a ship is ready to sail, requiring all crew members and passengers to return on board.
- 1851, W.H.G. Kingston, Peter the Whaler:
- We lay out in the stream for another whole day, with the Blue Peter flying, to show that we were ready for sea, and to summon any passengers who might yet remain on shore.
- 1881, Robert Louis Stevenson, Virginibus Puerisque:
- If we clung as devotedly as some philosophers pretend we do to the abstract idea of life, or were half as frightened as they make out we are, for the subversive accident that ends it all, the trumpets might sound by the hour and no one would follow them into battle - the blue-peter might fly at the truck, but who would climb into a sea-going ship?
- (card games, intransitive) In whist, a play that calls for trumps by throwing away a higher card of a suit while holding a lower one.
- The American coot, Fulica americana.