1815, "to say bad words, use profane language," a vulgar pronunciation of curse (v.). The transitive sense of "to curse, swear at" is by 1838. Related: Cussed; cussing. To cuss (someone) out is attested by 1881.
The loss of -r- before -s- is not uncommon: Compare arse/ass (n.2), burst/bust, horse/hoss, barse/bass, garsh/gash, parcel/passel.
1530s, from Latin tropus "a figure of speech," from Greek tropos "a turn, direction, course, way; manner, fashion," in rhetoric, "turn or figure of speech," related to trope "a turning" and trepein "to turn," from PIE root *trep- "to turn." Technically, in rhetoric, "a figure of speech which consists in the use of a word or phrase in a sense other than that which is proper to it" [OED], "as when we call a stupid fellow an ass, or a shrewd man a fox" [Century Dictionary].
c. 1300, "to try, endeavor, strive; test the quality of," from Anglo-French assaier, from assai (n.), from Old French assai, variant of essai "trial" (see essay (n.)). Related: Assayed; assaying.
1714, "contract between the King of Spain and another power," especially that made at the Peace of Utrecht, 1713, with Great Britain for furnishing African slaves to the Spanish colonies in the Americas (abrogated in 1750), from Spanish asiento, formerly assiento "a compact or treaty; a seat in court, a seat," from asentar/assentar "to adjust, settle, establish," literally "to place on a seat," from a sentar, from Latin ad "to" (see ad-) + sedens, present participle of sedere "to sit" (from PIE root *sed- (1) "to sit").
c. 1300, "to transfer, convey, bequeath (property); appoint (to someone a task to be done); order, direct (someone to do something); fix, settle, determine; appoint or set (a time); indicate, point out," from Old French assigner "assign, set (a date, etc.); appoint legally; allot" (13c.), from Latin assignare/adsignare "to mark out, to allot by sign, assign, award," from ad "to" (see ad-) + signare "make a sign," from signum "identifying mark, sign" (see sign (n.)). Its original use was in legal transfers of personal property. Related: Assigned; assigning.
"to soften," usually figuratively, of pain, anger, passion, grief, etc., c. 1300, from Anglo-French assuager, Old French assoagier "soften, moderate, alleviate, calm, soothe, pacify," from Vulgar Latin *adsuaviare, from Latin ad "to" (see ad-) + suavis "sweet, agreeable" (from PIE root *swād- "sweet, pleasant;" see sweet (adj.)). For sound development in French, compare deluge from Latin diluvium, abridge from abbreviare. Related: Assuaged; assuaging.
Middle English, from Latin Assyria, from Greek Assyria, short for Assyria ge "the Assyrian land," from fem. of Assyrios "pertaining to Assyria," from Akkadian Ashshur, name of the chief city of the kingdom and also of a god, probably from Assyrian sar "prince." Compare Syria. Related: Assyrian.
"diligence," early 15c., from Latin assiduitatem (nominative assiduitas) "continual presence," noun of quality from assiduus "continually present" (see assiduous).
Industry keeps at work, leaving no time idle. Assiduity (literally, a sitting down to work) sticks quietly to a particular task, with the determination to succeed in spite of its difficulty, or to get it done in spite of its length. Application, literally, bends itself to its work, and is, more specifically than assiduity, a steady concentration of one's powers of body and mind .... [Century Dictionary]
early 14c., assignacioun, "appointment by authority," from Old French assignacion (14c., Modern French assignation), from Latin assignationem (nominative assignatio) "an assigning, allotment," noun of action from past-participle stem of assignare/adsignare "to mark out, to allot by sign, assign, award," from ad "to" (see ad-) + signare "make a sign," from signum "identifying mark, sign" (see sign (n.)).
The meaning "action of legally transferring" (a right or property) is from 1570s; that of "a meeting by arrangement, tryst" is from 1650s, especially for a love-affair; assignation-house (1849) was an old euphemism for "brothel."
mid-15c., assistent "one who helps or aids another," from Latin assistentem (nominative assistens), noun use of present participle of assistere "stand by, attend" (see assist (v.)). The spelling changed in French then (16c.) in English.