early 14c., transitive ("collect into one place") and intransitive ("meet or come together"), from Old French assembler "come together, join, unite; gather" (11c.), from Latin assimulare "to make like, liken, compare; copy, imitate; feign, pretend," later "to gather together," from assimilated form of ad "to" (see ad-) + simulare "to make like," from stem of similis "like, resembling, of the same kind" (see similar).

In Middle English and in Old French it also was a euphemism for "to couple sexually." The meaning "put parts together" in manufacturing is from 1852. Related: Assembled; assembling. Assemble together is redundant.

"attentive, devoted, constant in application," 1530s, from Latin assiduus "attending; continually present, incessant; busy; constant," from assidere/adsidere "to sit down to, sit by" (thus "be constantly occupied" at one's work); from ad "to" (see ad-) + sedere "to sit" (from PIE root *sed- (1) "to sit"). The word acquired a taint of "servile" in 18c. Related: Assiduously; assiduousness.

1727, "resemblance of sounds between words other than rhyme," from French assonance, from assonant, from Latin assonantem (nominative assonans), present participle of assonare/adsonare "to resound, respond," from ad "to" (see ad-) + sonare "to sound" (from PIE root *swen- "to sound").

The more specific sense in prosody of "rhyming or correspondence of accented vowels but not consonants" is from 1823. In 20c. the sense tended to merge with consonance in the notion of slant rhyme, off rhyme, but properly there is a distinction.

Assonance is the relationship between words with different consonants immediately preceding and following the last accented vowels, which vowels have identical sounds (hit/will, disturb/bird, absolute/unglued). Consonance is the relationship between words whose final accented vowel sounds are different but with the same consonant frame (truck/trick, billion/bullion, impelling/compiling, trance/trounce). [Miller Williams, "Patterns of Poetry"]

c. 1300, "a gathering of persons, a group gathered for some purpose," from Old French asemblee, assemblee "assembly, gathering; union, marriage," noun use of fem. past participle of assembler "to assemble" (see assemble). The meaning "a gathering together" is recorded from early 15c.; that of "act of assembling parts or objects" is from 1914, as is assembly line.

Perhaps the most interesting department in the whole factory, to the visitor, is the final assembly. In this division, all the assembled units meet the assembly conveyor at the point where they are needed. At the start of the track a front axle unit, a rear axle unit and a frame unit are assembled. This assembly is then started in motion by means of a chain conveyor, and as it moves down the room at a constant speed of eight feet per minute, each man adds one part to the growing chassis or does one operation, which is assigned to him, so that when the chassis reaches the end of the line, it is ready to run on its own power. ["The Story of an Automobile Factory," in "Universal Book of Knowledge and Wonders," 1917]

The school sense, "gathering of all students for a presentation," is from 1932. Attested from mid-14c. as "a gathering for deliberation," hence its use as the name of the lower house in some state (earlier colonial) legislatures in America (1680s). In 17c.-18c., assemblies "dancing balls 'among polite persons of both sexes,' often paid for by subscription of the participants" were a prominent feature of social life.

a 19c. artificial singular of assets (q.v.).

"one who advocates racial or ethnic integration," 1900, originally in reference to Hawaii and possessions obtained by the U.S. in the war against Spain; later with reference to Jews in European nations; see assimilation + -ist. In Portuguese, assimilado (literally "assimilated," past participle of assimilar) was used as a noun of natives of the Portuguese colonies in Africa who were admitted to equal rights and citizenship.

1530s, "action of coming together for a common purpose," from Medieval Latin associationem (nominative associatio), noun of action from past-participle stem of associare "join with," from assimilated form of ad "to" (see ad-) + sociare "unite with," from socius "companion, ally" (from PIE *sokw-yo-, suffixed form of root *sekw- (1) "to follow").

The meaning "an organized body of persons with a common purpose" is from 1650s. The sense of "mental connection" is from 1680s; that of "quality or thing called to mind by something else" is from 1810.

"consisting of selected kinds arranged in sorts," 1797, past-participle adjective from assort (v.).

late 14c., "formal or solemn pledge, promise," also "certainty, full confidence," from Old French asseurance "assurance, promise; truce; certainty, safety, security" (11c., Modern French assurance), from asseurer "to reassure, to render sure" (see assure). The meaning "self-confident" is from 1590s. The word had a negative tinge 18c., often suggesting impudence or presumption.

early 14c., "consent, approval," from Old French assent, a back-formation from assentir "to agree" (see assent (v.)). "Assent is primarily an act of the understanding; consent is distinctly the act of the will: as, I assent to that proposition; I consent to his going" [Century Dictionary].