Etymology
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prefix (n.)

in grammar, "word or syllable or two syllables (rarely more) affixed to the beginning of a word to qualify its meaning or direct its application," 1640s, from Latin praefixum, noun use of neuter past participle of praefigere "fix in front, fasten on before," from prae "before" (see pre-) + root of figere "to fasten, fix" (from PIE root *dheigw- "to stick, fix"). Related: Prefixal.

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prefix (v.)

early 15c., prefixen, "appoint beforehand," from Old French prefixer, from pre- "before" (see pre-) + *fixer (see fix (v.)). Also compare Latin praefixus, past participle of praefigere. Meaning "to place at the beginning" is from 1530s; of words or parts of words from c. 1600. Related: Prefixed; prefixing.

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*dheigw- 

Proto-Indo-European root meaning "to stick, fix." 

It forms all or part of: affix; crucifix; crucify; dig; dike; ditch; fibula; fiche; fichu; fix; fixate; fixation; fixity; fixture; infibulate; infibulation; microfiche; prefix; suffix; transfix.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit dehi- "wall;" Old Persian dida "wall, stronghold, fortress," Persian diz; Latin figere "to fix, fasten, drive, thrust in; pierce through, transfix;" Lithuanian dygstu, dygti "germinate;" Old Irish dingid "presses, thrusts down;" Old English dic "trench, ditch," Dutch dijk "dam." 

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an- (1)
privative prefix, from Greek an-, "not, without," from PIE root *ne- "not"). The Greek prefix is a fuller form of the one represented in English by a- (3).
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on- 

the preposition and adverb on used as a prefix; Old English on-, an-.

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pur- 

Middle English and Anglo-French perfective prefix, corresponding to Old French por-, pur- (Modern French pour), from Vulgar Latin *por-, a variant of Latin pro "before, for" (see pro-). This is the earliest form of the prefix in English, and it is retained in some words, but in others it has been corrected to Latinate pro-.

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il- 
assimilated form of Latin prefix in- used with words beginning in l-; see in-.
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cross- 

word-forming element typically representing cross as a noun, adverb (cross-examine), adjective (crossbar), and in many words a confluence of them. "There is no distinct line of division between cross as an adjective and cross as a prefix. As a prefix, it often represents the adv. cross, or the prep. cross, across." [Century Dictionary]

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ashram (n.)
"religious hermitage," 1900, from Sanskrit asramah, from a-, adnomial prefix (from PIE adverbial particle ē), + sramah "effort, toll, fatigue."
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gazillion (n.)

by 1984, with made-up prefix and ending from billion, trillion, etc. Perhaps based on earlier zillion.

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