specialist (n.)

c. 1200, "given or granted in unusual circumstances, exceptional;" also "specific" as opposed to general or common; from Old French special, especial "special, particular, unusual" (12c., Modern French spécial) and directly from Latin specialis "individual, particular" (source also of Spanish especial, Italian speziale), from species "appearance, kind, sort" (see species).

The meaning "marked off from others by some distinguishing quality; dear, favored" is recorded from c. 1300. Also from c. 1300 is the sense of "selected for an important task; specially chosen." It is attested from mid-14c. as "extraordinary, distinguished, having a distinctive character," on the notion of "used for special occasions;" hence "excellent; precious."

From late 14c. as "individual, particular; characteristic." The specific meaning "limited as to function, operation, or purpose" is from 14c., but developed especially in the 19c.; the sense of "in addition to the usual or ordinary" (as in special edition) is by 1840.

Special effects in the Hollywood sense is by 1922, produced in the theater, not the studio:

Many were the well-deserved congratulations received by Mr. Charles Williams regarding the wonderful presentation of "The Four Horsemen of the Apocalypse" at the Futurist, Birmingham. The special effects included rain produced by sprinklers, the noises of the battlefield by the aid of blank maroons and revolver cartridges, and orchestral effects under the guidance of Mr. Alex Cohen which undoubtedly contributed largely to the marked success of the presentation. [The Film Renter & Moving Picture News, Dec. 16, 1922]

Special interest in the U.S. political sense of "group or industry seeking advantages for itself" is from 1910. Special education in reference to teaching those whose learning is impeded by some mental or physical handicap is from 1972. Special pleading is recorded by 1680s, a term that had a sound legal meaning once but now is used generally and imprecisely.

Special pleading. (a) The allegation of special or new matter, as distinguished from a direct denial of matter previously alleged on the other side. ... (c) In popular use, the specious but unsound or unfair argumentation of one whose aim is victory rather than truth. [Century Dictionary]

1610s, "one who generalizes," from general (adj.) + -ist. From 1894 as "one who engages in general studies" (opposed to specialist).

word-forming element meaning "one who does or makes," also used to indicate adherence to a certain doctrine or custom, from French -iste and directly from Latin -ista (source also of Spanish, Portuguese, Italian -ista), from Greek agent-noun ending -istes, which is from -is-, ending of the stem of verbs in -izein, + agential suffix -tes.

Variant -ister (as in chorister, barrister) is from Old French -istre, on false analogy of ministre. Variant -ista is from Spanish, popularized in American English 1970s by names of Latin-American revolutionary movements.