late 14c., publike, "open to general observation," from Old French public (c. 1300) and directly from Latin publicus "of the people; of the state; done for the state," also "common, general, of or belonging to the people at large; ordinary, vulgar," and as a noun, "a commonwealth; public property." This Latin word was altered (probably by influence of Latin pubes "adult population, adult;" see pubis) from Old Latin poplicus "pertaining to the people," from populus "people" (see people (n.)).
Attested in English from early 15c. as "of or pertaining to the people at large" and from late 15c. as "pertaining to public affairs." The meaning "open to all in the community, to be shared or participated in by people at large" is from 1540s in English. An Old English adjective in this sense was folclic. The sense of "done or made by or on behalf of the community as a whole" is by 1550s; that of "regarding or directed to the interests of the community at large, patriotic" is from c. 1600.
Public relations "the management of the relationship between a company or corporation and the general public" is recorded by 1913 (with an isolated use by Thomas Jefferson in 1807). Public office "position held by a public official" is from 1821; public service is from 1570s; public interest "the common well-being" is from 1670s. Public enemy, one considered a nuisance to the general community, is attested from 1756. Public sector attested from 1949. Public funds (1713) are the funded debts of a government.
Public woman "prostitute" is by 1580s, on the notion of "open for the use of all." For public house, see pub.