by 1993, from fashion + -ista (see -ist). In the same sense were fashionist ("obsequious follower of modes and fashions," 1610s, alive as late as 1850); fashion-monger (1590s); fashion-fly (1868).
Entries linking to fashionista
fashion n.
c. 1300, fasoun, "physical make-up or composition; form, shape; appearance," from Old French façon, fachon, fazon "face, appearance; construction, pattern, design; thing done; beauty; manner, characteristic feature" (12c.), from Latin factionem (nominative factio) "a making or doing, a preparing," also "group of people acting together," from facere "to make" (from PIE root *dhe- "to set, put").
Especially "style, manner" of make, dress, or embellishment (late 14c.); hence "prevailing custom; mode of dress and adornment prevailing in a place and time" (late 15c.). Meaning "good style, conformity to fashionable society's tastes" is from 1630s.
To call a fashion wearable is the kiss of death. No new fashion worth its salt is wearable. [Eugenia Sheppard, New York Herald Tribune, Jan. 13, 1960]
In Middle English also spelled faschyoun, facune, faction, etc. Fashion plate (1851) originally was "full-page picture in a popular magazine showing the prevailing or latest style of dress," in reference to the typographic plate from which it was printed. Transferred sense of "well-dressed person" had emerged by 1920s. After a fashion "to a certain extent" is from 1530s. Shakespeare (c. 1600) has both in fashion and out of fashion.
-ist
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.