essayist (n.)

1590s, "trial, attempt, endeavor," also "short, discursive literary composition" (first attested in writings of Francis Bacon, probably in imitation of Montaigne), from French essai "trial, attempt, essay" (in Old French from 12c.), from Late Latin exagium "a weighing, a weight," from Latin exigere "drive out; require, exact; examine, try, test," from ex "out" (see ex-) + agere "to set in motion, drive" (from PIE root *ag- "to drive, draw out or forth, move") apparently meaning here "to weigh." The suggestion is of unpolished writing. Compare assay, also examine.

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.