In English, parousia is a learned theological noun. It names the expected return of Christ at the end of history, the event more often called the Second Coming. That is the sense desk dictionaries treat as ordinary. A much rarer philosophical use, the presence of a form or idea in a particular thing, is listed in some English dictionaries but is seldom met outside specialist prose. The word is usually lowercase in running text, though many writers still capitalize it as a doctrinal title.
The origin of the word parousia is not a native English story. English did not inherit the form from Old English or from French. It is a direct learned borrowing of Ancient Greek παρουσία, whose everyday meaning was presence: the state of being at hand rather than away. Nineteenth-century desk dictionaries commonly date the English borrowing to the years around 1870–75 and point to the New Testament, especially the discourse in Matthew 24 that asks about the coming of the Son of Man. Merriam-Webster, working from a different first-citation file, puts the earliest English use earlier, in 1781. The sources disagree about when English printers first needed the Greek term as an English word. They do not disagree about what the Greek meant.
Being beside
The morphology is transparent once the Greek is taken apart, though handbooks slice the same string two ways. One analysis starts from παροῦσα, the feminine present participle of πάρειμι, to be present, and adds the abstract suffix -ία. Presence is named as a state. Another, common in English etymological notes, reads the noun as παρά plus οὐσία, being or essence, with the same abstract ending. Those are not rival histories so much as two cuts through one formation. The verb πάρειμι itself is παρά, beside or near, plus εἰμί, to be. The picture underneath is not travel from a distance but being-alongside: someone who has arrived and is now there.
The being half sits on the same Indo-European root as English is and Latin esse. The beside half is the Greek para- familiar from parallel and paradox. English presence, from Latin praesentia, is a semantic cousin rather than a sound-cognate: another language’s way of saying being-at-hand. The Greek antonym ἀπουσία, absence, shows the same architecture with a different prefix. Readers of Greek can still feel that pair even when the English noun no longer means either presence or absence in ordinary speech.
A visit, not a mood
Classical authors from the tragedians, Thucydides, and Plato onward use παρουσία for presence as opposed to absence, and then for arrival. In Hellenistic Greek, especially in Ptolemaic Egypt, the noun became a quasi-official label for the visit of a king, an emperor, or a high official. Documentary papyri record grain levies, crown gifts, and food laid in for such a visit. The visit reorganized a town’s supplies for a few days and advertised the ruler’s personal presence. It was an event, not a mood.
New Testament writers knew both layers. Paul can speak of his own παρουσία in a church as simply being there in the body, set against absence. The same noun, in the same corpus, is also the technical name for Christ’s future advent: a coming that is not a rumor or a letter but a personal arrival. Later church Greek could mark that event as a second παρουσία, in contrast with the first, the incarnation already past. English, borrowing the word late and almost only for church use, kept nearly the second of those layers. Ordinary presence already had a native and a Latin vocabulary. What English needed was a compact label for a debated eschatological event. Once the term sat in theological English, it could be distinguished from neighboring Greek loans such as epiphany, and from advent, which English had already taken through Latin.
A spelling variant parusia, from a modern Latin wrapping of the same Greek, also appears as a rhetorical term: the device of using a present tense where a past or future would be expected, for dramatic effect. That is a side path. It shows that the Greek noun kept traveling through learned Latin, but it is not the main English career of parousia.
What later languages kept
Modern descendants keep the older Greek sense more faithfully than English does. Contemporary Greek παρουσία still means presence in ordinary speech. French parousie, German Parusie, Spanish parusía, and Polish paruzja follow the theological borrowing. English is the outlier: it took a common Greek noun of attendance and arrival and narrowed it, in everyday use, to one doctrinal moment.
The useful historical residue is the royal visit. Read only as a synonym for Second Coming, the English noun sounds like a uniquely Christian invention. Read against the papyri, it is the old name for a ruler who does not send a deputy but arrives in person, and whose arrival is itself the event that changes the room.