The earliest use of privacy in the OED appears in the 17th century. According to Google books Ngram Viewer it constituted 0.000432% (which I will hereafter show as 4.32/10K) of words in books around 1600. By 1605 it no longer appears in Ngram until 1641 when it reappears at 0.14/10K rising to 7.37/10K in 1664. It then fell to 3.16/10K in 1700 and 2.33/10K in 1720 where it bumped around 2.5/10K for the next two centuries with a high of 3.28 in 1824.
In 1890 Brandeis and Warren published “The Right to Privacy” in the Harvard Law Review. In 1928 Brandeis wrote a dissent in the case of Olmstead v. U.S. in which he argued that the warrantless wiretapping of a bootlegger constituted a violation of his right to privacy:
Whenever a telephone line is tapped, the privacy of the persons at both ends of the line is invaded and all conversations between them upon any subject, and, although proper, confidential and privileged, may be overheard. Moreover, the tapping of one man’s telephone line involves the tapping of the telephone of every other person whom he may call or who may call him. As a means of espionage, writs of assistance and general warrants are but puny instruments of tyranny and oppression when compared with wire-tapping…
(The makers of our Constitution) conferred, as against the Government, the right to be let alone—the most comprehensive of rights and the right most valued by civilized men. To protect that right, every unjustifiable intrusion by the Government upon the privacy of the individual, whatever the means employed, must be deemed a violation of the Fourth Amendment. And the use, as evidence in a criminal proceeding, of facts ascertained by such intrusion must be deemed a violation of the Fifth.
But it was not until Griswold v. Connecticut in 1965 that the Supreme Court recognized “that specific guarantees in the Bill of Rights have penumbras, formed by emanations from those guarantees that help give them life and substance” to overrule a Connecticut law prohibiting the prescription and sale of birth control devices violating the right of marital privacy. Soon after in 1967 Olmstead was overruled in Katz v. U. S.
What brought about that change of opinion? In 1920 the use of the word privacy began an exponential increase from 2.68/10K in 1920 to 4.14/10K in 1950 to 7.55/10K in 1970 to 14.19/10K in 1990 cresting at 21.01/10K in 2003 before declining to 18.9/10K in 2008 (the latest year available). This tracks to the number of automobiles per person which grew from 86/1,000 people in 1920 to 286/K in 1950 to 478/K in 1970 to 717/K in 1990 cresting at 823/K in 2007 and declining to 801/K in 2012. Not a coincidence as the automobile brought greater freedom of movement to almost every American than had ever existed for any person before. With that freedom of movement came the ability to quickly go to strange communities with greater anonymity. And the ability to commute from the suburbs, where people no longer lived cheek by jowl in multi-family dwellings with attached walls or as part of an integrated rural community.
So what is happening to our concept of privacy with word frequency 10% in five years from 2003 to 2008? Perhaps it has something to do with the decline in popularity of driving among the young. The percentage of 25-29 year olds holding drivers licenses declined from 94% in 1994 to 90% in 2002 to 86% in 2012. Or the growth of American Facebook users from 1 million at the end of 2004 to 169 million in 2013. And the willingness of those users to make public virtually anything about themselves for the world to see and even more about their friends.
Considering that it took only 39 years for wire tapping to go from being morally questionable but not illegal to being unconstitutional, it will be interesting to see how our concept of a right to privacy evolves.