1550s, "dispossessed," past-participle adjective from deprive. As a euphemism for the condition of children who lack a stable home life, by 1945.

late 14c., "pertaining or belonging to oneself, not shared, peculiar to an individual only;" of a thing, "not open to the public, for the use of privileged persons;" of a religious rule, "not shared by Christians generally, distinctive;" from Latin privatus "set apart (from what is public), belonging to oneself (not to the state), peculiar, personal," used in contrast to publicus, communis.

This is a past-participle adjective from the verb privare "to bereave, deprive, rob, strip" of anything; "to free, release, deliver" from anything, from privus "one's own, individual," from Proto-Italic *prei-wo- "separate, individual," from PIE *prai-, *prei- "in front of, before," from root *per- (1) "forward." The semantic shift would be from "being in front" to "being separate."

Old English in this sense had syndrig. Of persons, "not holding public office or employment," recorded from early 15c. Of communications, "meant to be secret or confidential," 1550s. In private "privily" is from 1580s. Related: Privately.

Private school "school owned and run by individuals, not by the government, and run for profit" is by 1650s. Private parts "the pudenda" is from 1785 (privete "the sexual parts" is from late 14c.; secret parts in the same sense is from 16c.).

Private property "property of persons in their individual, personal, or private capacity," as distinguished from property of the state or public or for public use, is by 1680s. Private enterprise "business or commercial activity privately owned and free from direct state control" is recorded by 1797; private sector "part of an economy, industry, etc. that is free from state control" is from 1948.

Private eye "private detective, person engaged unofficially in obtaining secret information for or guarding the private interests of those who employ him" is recorded from 1938, American English (Chandler). Private detective "detective who is not a member of an official police force" is by 1856.

active word-forming element in English and in many verbs inherited from French and Latin, from Latin de "down, down from, from, off; concerning" (see de), also used as a prefix in Latin, usually meaning "down, off, away, from among, down from," but also "down to the bottom, totally" hence "completely" (intensive or completive), which is its sense in many English words.

As a Latin prefix it also had the function of undoing or reversing a verb's action, and hence it came to be used as a pure privative — "not, do the opposite of, undo" — which is its primary function as a living prefix in English, as in defrost (1895), defuse (1943), de-escalate (1964), etc. In some cases, a reduced form of dis-.

Proto-Indo-European root forming prepositions, etc., meaning "forward," and, by extension, "in front of, before, first, chief, toward, near, against," etc.

It forms all or part of: afford; approach; appropriate; approve; approximate; barbican; before; deprive; expropriate; far; first; for; for-; fore; fore-; forefather; foremost; former (adj.); forth; frame; frau; fret; Freya; fro; froward; from; furnish; furniture; further; galore; hysteron-proteron; impervious; improbity; impromptu; improve; palfrey; par (prep.); para- (1) "alongside, beyond; altered; contrary; irregular, abnormal;" paradise; pardon; paramount; paramour; parvenu; pellucid; per; per-; percent; percussion; perennial; perestroika; perfect; perfidy; perform; perfume; perfunctory; perhaps; peri-; perish; perjury; permanent; permeate; permit; pernicious; perpendicular; perpetual; perplex; persecute; persevere; perspective; perspire; persuasion; pertain; peruse; pervade; pervert; pierce; portray; postprandial; prae-; Prakrit; pre-; premier; presbyter; Presbyterian; preterite; pride; priest; primal; primary; primate; primavera; prime; primeval; primitive; primo; primogenitor; primogeniture; primordial; primus; prince; principal; principle; prior; pristine; private; privilege; privy; pro (n.2) "a consideration or argument in favor;" pro-; probably; probe; probity; problem; proceed; proclaim; prodigal; produce; profane; profess; profile; profit; profound; profuse; project; promise; prompt; prone; proof; proper; property; propinquity; prophet; prose; prostate; prosthesis; protagonist; Protean; protect; protein; Proterozoic; protest; proto-; protocol; proton; protoplasm; Protozoa; proud; prove; proverb; provide; provoke; prow; prowess; proximate; Purana; purchase; purdah; reciprocal; rapprochement; reproach; reprove; veneer.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit pari "around, about, through," parah "farther, remote, ulterior," pura "formerly, before," pra- "before, forward, forth;" Avestan pairi- "around," paro "before;" Hittite para "outside of," Greek peri "around, about, near, beyond," pera "across, beyond," paros "before," para "from beside, beyond," pro "before;" Latin pro "before, for, on behalf of, instead of," porro "forward," prae "before," per "through;" Old Church Slavonic pra-dedu "great-grandfather;" Russian pere- "through;" Lithuanian per "through;" Old Irish ire "farther," roar "enough;" Gothic faura "before," Old English fore (prep.) "before, in front of," (adv.) "before, previously," fram "forward, from," feor "to a great distance, long ago;" German vor "before, in front of;" Old Irish air- Gothic fair-, German ver-, Old English fer-, intensive prefixes.