resort n.

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]

"attack of the besieged upon the besiegers," 1778, from French sortie (16c.), literally "a going out," noun use of fem. past participle of sortir "go out," from Vulgar Latin *surctire, from Latin surrectus, past participle of surgere "rise up" (see surge (n.)). Extended in World War I to operational flights by military aircraft (1918).

late 14c., sorte, "group of people, animals, etc.; kind or variety of person or animal," from Old French sorte "class, kind," from Latin sortem (nominative sors) "lot; fate, destiny; share, portion; rank, category; sex, class, oracular response, prophecy," from PIE root *ser- (2) "to line up."

The sense evolution in Vulgar Latin is from "what is allotted to one by fate," to "fortune, condition," to "rank, class, order." Later (mid-15c.) also "group, class, or category of items; kind or variety of thing; pattern, design." The classical sense of "fate or lot of a particular person" was in Middle English but is now obsolete. The computing sense of "act of arranging (data) in sequence" is by 1958, from the verb. Related to assort, consort, sorcery, but not resort.

Colloquial sort of as a qualifier expressing hesitation or "to some extent" is attested by 1790; sometimes contracted to sorta, sorter. Out of sorts "not in usual good condition" is attested from 1620s, perhaps with a literal sense of "out of stock, out of equipment." In the original citation it is paired with out of tune. The type-setting sort is attested only from 1660s.