rework v.

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]

a fusion of Old English wyrcan (past tense worhte, past participle geworht) "prepare, perform, do, make, construct, produce; strive after" (from Proto-Germanic *wurkjanan); and Old English wircan (Mercian) "to operate, function, set in motion," a secondary verb formed relatively late from Proto-Germanic noun *werkan (see work (n.)).

Sense of "perform physical labor" was in Old English, as was sense "ply one's trade" and "exert creative power, be a creator." Transitive sense "manipulate (physical substances) into a desired state or form" was in Old English. Meaning "have the expected or desired effect" is from late 14c. In Middle English also "perform sexually" (mid-13c.). Related: Worked (15c.); wrought; working.

To work in "insert, introduce or intermix, as one material with another," is by 1670s; hence the figurative sense "cause to enter or penetrate by repeated efforts." To work up (transitive) "bring into some state or condition" is by 1590s of material things, 1690s of immaterial things; hence "bring by labor or special effort to a higher state or condition" (1660s). The meaning "excite, stir up, raise, rouse" is from c. 1600. To work over "beat up, thrash" is from 1927. To work against "attempt to subvert" is from late 14c.

To work out "bring about or procure (a result) by continued labor or effort" is by 1530s. As "bring to a fuller or finished state, elaborate, develop," by 1821. Meaning "to solve, calculate the solution to" a problem or question is by 1848. Intransitive sense "make its way out" is from c. 1600; the sense of "succeed" is attested by 1909. Sense of "exhaust (a mine, etc.) by working it" is from 1540s. The pugilistic sense of "box for practice" (rather than in a contest) is by 1927, hence the general sense of "practice, rehearse" (1929) and that of "take exercise" (by 1948).