fashionable adj.

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.

common termination and word-forming element of English adjectives (typically based on verbs) and generally adding a notion of "capable of; allowed; worthy of; requiring; to be ______ed," sometimes "full of, causing," from French -able and directly from Latin -abilis. It is properly -ble, from Latin -bilis (the vowel being generally from the stem ending of the verb being suffixed), and it represents PIE *-tro-, a suffix used to form nouns of instrument, cognate with the second syllables of English rudder and saddle (n.).

A living element in English, used in new formations from either Latin or native words (readable, bearable) and also with nouns (objectionable, peaceable). Sometimes with an active signification (suitable, capable), sometimes of neutral signification (durable, conformable). It has become very elastic in meaning, as in a reliable witness, a playable foul ball, perishable goods. A 17c. writer has cadaverable "mortal."

To take a single example in detail, no-one but a competent philologist can tell whether reasonable comes from the verb or the noun reason, nor whether its original sense was that can be reasoned out, or that can reason, or that can be reasoned with, or that has reason, or that listens to reason, or that is consistent with reason; the ordinary man knows only that it can now mean any of these, & justifiably bases on these & similar facts a generous view of the termination's capabilities; credible meaning for him worthy of credence, why should not reliable & dependable mean worthy of reliance & dependence? [Fowler]

In Latin, -abilis and -ibilis depended on the inflectional vowel of the verb. Hence the variant form -ible in Old French, Spanish, English. In English, -able tends to be used with native (and other non-Latin) words, -ible with words of obvious Latin origin (but there are exceptions). The Latin suffix is not etymologically connected with able, but it long has been popularly associated with it, and this probably has contributed to its vigor as a living suffix.

1560s, "incapable of being shaped," from un- (1) "not" + fashionable. Meaning "not in accordance with prevailing fashion" is attested from 1640s. Related: Unfashionably.