"imaginary average American citizen," 1934; the Q perhaps suggested by John Quincy Adams.
1940, from George H. Gallup (1901-1984), U.S. journalist and statistician, who in 1935 set up the American Institute of Public Opinion.
"the executive branch of the public service," as distinguished from the military, naval, legislative, or judicial, 1765, originally in reference to non-military staff of the East India Company, from civil in the sense "not military." Civil servant is from 1792.
older uses refer to schools in Ireland begun 1733 by the Charter Society to provide Protestant education to poor Catholic children. Modern use in U.S. began c. 1988, as an alternative to state-run public education. See charter (n.).
type of hawk that is believed to prey on domestic fowl, 1802, American English. Figuratively, from the secondary senses of both words, "public person who advocates war but declined significant opportunity to serve in uniform during wartime," at least 1988, American English. From chicken (n.) + hawk (n.).
1650s, "public department in charge of letter-carrying," from post (n.3) + office. Meaning "building where postal business is carried on, office or place where letters are received for transmission," is from 1650s. In slang or euphemistic sense of "a sexual game" it refers to an actual parlor game first attested early 1850s in which pretend "letters" were paid for by kisses.
It is clear that none of the unfortunate people, perhaps at this moment on board, can stand upright, but that they must sit down, and contract their limbs within the limits of little more than three square feet, during the whole of the middle passage. I cannot compare the scene on board this vessel, to any other than that of a pen of sheep; with this difference only, that the one have the advantages of a wholesome air, while that, which the others breathe, is putrid. [Thomas Clarkson, "An Essay on the Slavery and Commerce of the Human Species," 1788]