Etymology
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police (n.)
Origin and meaning of police

1530s, "the regulation and control of a community" (similar in sense to policy (n.1)); from Middle French police "organized government, civil administration" (late 15c.), from Latin politia "civil administration," from Greek polis "city" (see polis).

Until mid-19c. used in England for "civil administration;" application to "administration of public order, law-enforcement in a community" (1716) is from French (late 17c.), and originally in English referred to France or other foreign nations.

The sense of "an organized civil force for maintaining order, preventing and detecting crime, etc." is by 1800; the first force so-named in England was the Marine Police, set up 1798 to protect merchandise at the Port of London. Meaning "body of officers entrusted with the duty of enforcing laws, detecting crime, etc." is from 1810.

In its most common acceptation, the police signifies the administration of the municipal laws and regulations of a city or incorporated town or borough by a corps of administrative or executive officers, with the necessary magistrates for the immediate use of force in compelling obedience and punishing violation of the laws, as distinguished from judicial remedies by action, etc. The primary object of the police system is the prevention of crime and the pursuit of offenders; but it is also subservient to other purposes, such as the suppression of mendicancy, the preservation of order, the removal of obstructions and nuisances, and the enforcing of those local and general laws which relate to the public health, order, safety, and comfort. [Century Dictionary, 1895]

In constitutional law, police power is the power of a government to limit civil liberties and exercise restraint and compulsion over private rights, especially to advance or protect the public welfare. Police state "state regulated by means of national police" first recorded 1865, with reference to Austria. Police action in the international sense of "military intervention short of war, ostensibly to correct lawlessness" is from 1933. Police officer is attested from 1794, American English. Police station is from 1817. Police dog is by 1908.

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re- 

word-forming element meaning "back, back from, back to the original place;" also "again, anew, once more," also conveying the notion of "undoing" or "backward," etc. (see sense evolution below), c. 1200, from Old French re- and directly from Latin re- an inseparable prefix meaning "again; back; anew, against."

Watkins (2000) describes this as a "Latin combining form conceivably from Indo-European *wret-, metathetical variant of *wert- "to turn." De Vaan says the "only acceptable etymology" for it is a 2004 explanation which reconstructs a root in PIE *ure "back."

In earliest Latin the prefix became red- before vowels and h-, a form preserved in redact, redeem, redolent, redundant, redintegrate, and, in disguise, render (v.). In some English words from French and Italian re- appears as ra- and the  following consonant is often doubled (see rally (v.1)).

The many meanings in the notion of "back" give re- its broad sense-range: "a turning back; opposition; restoration to a former state; "transition to an opposite state." From the extended senses in "again," re- becomes "repetition of an action," and in this sense it is extremely common as a formative element in English, applicable to any verb. OED writes that it is "impossible to attempt a complete record of all the forms resulting from its use," and adds that "The number of these is practically infinite ...."   

Often merely intensive, and in many of the older borrowings from French and Latin the precise sense of re- is forgotten, lost in secondary senses, or weakened beyond recognition, so that it has no apparent semantic content (receive, recommend, recover, reduce, recreate, refer, religion, remain, request, require). There seem to have been more such words in Middle English than after, e.g. recomfort (v.) "to comfort, console; encourage;" recourse (n.) "a process, way, course." Recover in Middle English also could mean "obtain, win" (happiness, a kingdom, etc.) with no notion of getting something back, also "gain the upper hand, overcome; arrive at;" also consider the legal sense of recovery as "obtain (property) by judgment or legal proceedings." 

And, due to sound changes and accent shifts, re- sometimes entirely loses its identity as a prefix (rebel, relic, remnant, restive, rest (n.2) "remainder," rally (v.1) "bring together"). In a few words it is reduced to r-, as in ransom (a doublet of redemption), rampart, etc.

It was used from Middle English in forming words from Germanic as well as Latin elements (rebuild, refill, reset, rewrite), and was used so even in Old French (regret, regard, reward, etc.).

Prefixed to a word beginning with e, re- is separated by a hyphen, as re-establish, re-estate, re-edify, etc. ; or else the second e has a dieresis over it: as, reëstablish, reëmbark, etc. The hyphen is also sometimes used to bring out emphatically the sense of repetition or iteration : as, sung and re-sung. The dieresis is not used over other vowels than e when re is prefixed : thus, reinforce, reunite, reabolish. [Century Dictionary, 1895]
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