privateyoudaoicibaDictYouDict[private 词源字典]
private: [14] Latin prīvus meant ‘single, individual’. From it was derived the verb prīvāre, source of English deprive [14] and privation [14]. This originally meant ‘make solitary, isolate’, and although it later moved on metaphorically to ‘bereave, deprive’, its earliest sense was preserved in the adjective formed from its past participle prīvātus.

This denoted ‘belonging to the individual alone’, hence ‘not belonging or related to the state’. English has acquired the word twice: first, via Old French, as the now almost archaic privy [13], and later, directly from Latin, as private. Privilege [12] comes via Old French privilege from Latin prīvilēgium, a compound formed from prīvus and lēx ‘law’ (source of English legal) which etymologically meant ‘law affecting an individual’.
=> deprive, privilege, privy[private etymology, private origin, 英语词源]
private (adj.)youdaoicibaDictYouDict
late 14c., "pertaining or belonging to oneself, not shared, individual; not open to the public;" of a religious rule, "not shared by Christians generally, distinctive; from Latin privatus "set apart, belonging to oneself (not to the state), peculiar, personal," used in contrast to publicus, communis; past participle of privare "to separate, deprive," from privus "one's own, individual," from PIE *prei-wo-, from PIE *prai-, *prei-, from root *per- (1) "forward, through" (see per).

Old English in this sense had syndrig. Private grew popular 17c. as an alternative to common (adj.), which had overtones of condescension. Of persons, "not holding public office," recorded from early 15c. In private "privily" is from 1580s. Related: Privately. Private school is from 1650s. Private parts "the pudenda" is from 1785. Private enterprise first recorded 1797; private property by 1680s; private sector is from 1948. Private eye "private detective" is recorded from 1938, American English.
private (n.)youdaoicibaDictYouDict
1590s, "private citizen," short for private person "individual not involved in government" (early 15c.), or from Latin privatus "man in private life," noun use of the adjective; 1781 in the military sense, short for Private soldier "one below the rank of a non-commissioned officer" (1570s), from private (adj.).