perfectionist n.

early 13c., perfeccioun, "consummate state or form, that degree of excellence which leaves nothing to be desired," from Old French perfection "perfection, completeness" (12c.), from Latin perfectionem (nominative perfectio) "a finishing, completing, perfection," noun of action from past-participle stem of perficere "to accomplish, finish, complete" (see perfect (adj.)).

From late 14c. as "flawlessness, correctness, purity," also "act of making perfect," also "state of being complete." The meaning "quality, endowment, or acquirement characterized by excellence or great worth or value" is from 1570s.

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.