I've checked the subreddit rules, and there doesn't seem to be anything regarding "clarifying questions." Regrettably, being an attorney, my natural inclination is to tell you "it depends."
Primarily, I'm not sure what you mean by a "literal interpretation" when "expectation of privacy" is just shorthand for "reasonable expectation of privacy." Given that the 4th Amendment of the US Constitution prohibits unreasonable searches and seizures by state actors, the definitions and contours of reasonableness are part of that literal interpretation.
To the extent we began using "reasonable expectations of privacy" as a term of art in case law, you are probably going to start at the 1967 case of Katz v. United States. However, before we can discuss Katz, we need to back up to Olmstead v. US, which was decided in 1928.
In the early 20th century, we began to see the advent of government surveillance through the use of wiretaps. Unlike the traditional search and seizure violations imagined by the drafters, wiretaps allowed the government to eavesdrop on conversations with greater secrecy and lack of physical intrusion. The 4th Amendment has never been self-defining, but as the nature of searches began to change alongside the technological landscape, potential violations manifested in ways that had not been envisioned and courts were stuck with articulating its contours in a modern context.
The issue in Olmstead was the applicability of the 4th amendment to this new technology, and the result was a narrow interpretation, with the Court holding that "[b]ecause the government did not physically trespass on the defendants’ property...there was no 'search' in a constitutional sense by the government." (see: Peter Winn, Katz and the Origins of the "Reasonable Expectation of Privacy" Test.)
By 1967, the use of wiretaps and phone interception was ripe for revisitation. The narrow decision of Olmstead was overturned, with the majority writing that the 4th Amendment "protects people, not places," although the ruling still made a "clear statement" about the "essential legality of electronic surveillance." Winn, Origins of REP Test.
The term "reasonable expectation of privacy" then appears in Justice Harlan's concurrence rather than the majority opinion:
I join the opinion of the Court, which I read to hold only (a) that an enclosed telephone booth is an area where, like a home, Weeks v. United States, 232 U.S. 383, and unlike a field, Hester v. United States, 265 U.S. 57, a person has a constitutionally protected reasonable expectation of privacy
Emphasis added.
He then expounds upon what constitutes a reasonable expectation:
As the Court's opinion states, "the Fourth Amendment protects people, not places." The question, however, is what protection it affords to those people. Generally, as here, the answer to that question requires reference to a "place." My understanding of the rule that has emerged from prior decisions is that there is a twofold requirement, first that a person have exhibited an actual (subjective) expectation of privacy and, second, that the expectation be one that society is prepared to recognize as "reasonable." Thus, a man's home is, for most purposes, a place where he expects privacy, but objects, activities, or statements that he exposes to the "plain view" of outsiders are not "protected," because no intention to keep them to himself has been exhibited. On the other hand, conversations in the open would not be protected against being overheard, for the expectation of privacy under the circumstances would be unreasonable. Cf. Hester v. United States, supra.
Since Katz, the Court has been unwilling to articulate any single test for reasonableness of an expectation of privacy (see: O'Connor v. Ortega, "We have no talisman that determines in all cases those privacy expectations that society is prepared to accept as reasonable"), but as far as historical roots in case law are concerned, the term of art itself pops up in Justice Harlan's Katz concurrence.
A few thoughts:
If you're talking about a broader "right to privacy" that commonly pops up in reproductive rights discussions, for example, you're going to want to know more about fundamental due process rights under the 14th Amendment. It's a separate strand of law that governs an entirely different host of issues that remains separate from the 4th's search and seizure restriction.
In terms of reasonable expectations of privacy in tort, that would vary from state-to-state. Because you specifically said "search and seizure," I limited this brief survey to the constitutional constraint on state action, not two civil litigants.
I'm adding these thoughts because, in my experience, because of the overlap in terms, many people confuse the applicability of the law between the 4th Amendment, 14th Amendment, and certain torts, all of which touch on privacy in some way but differ on, among other things, to whom they apply and what constitutes a violation/triggers liability.
Hope that answers your question.