mid-14c., confourmen, "be obedient (to God), comply," from Old French conformer "conform (to), agree (to), make or be similar, be agreeable" (13c.) and directly from Latin conformare "to fashion, to form, to shape; educate; modify," from assimilated form of com "together" (see con-) + formare "to form" (see form (v.)).

Meaning "to make of the same form or character; bring into harmony, make agreeable," and intransitive sense of "act in accordance with an example" are from late 14c. Sense of "to comply with the usages of the Church of England" is from 1610s; hence conformist (1630s), opposed to non-conformist or dissenter. Related: Conformance; conformed; conforming.

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.

1890, "tendency or need to conform" to some group standard, from conform + -ism. In religion, from c. 1902. In geology from c. 1912. Modern, general sociological sense (social conformism) popularized from c. 1948.

also non-conformist, "one who does not conform to some law or usage," 1610s, originally and especially of clergymen who adhered to Church of England doctrine but not its practice, from non- + conformist. After their ejection under the Act of Uniformity (1662) the name passed to the separate churches they joined or formed. In general use from 1670s as "one who does not participate in a practice or course of action." As an adjective from 1640s. Shortened form non-con is attested from 1680s.