Old English bisignes (Northumbrian) "care, anxiety, occupation," from bisig "careful, anxious, busy, occupied, diligent" (see busy (adj.)) + -ness. The original sense is obsolete, as is the Middle English sense of "state of being much occupied or engaged" (mid-14c.), the latter replaced by busyness. Johnson's dictionary also has busiless "At leisure; without business; unemployed." The modern two-syllable pronunciation is from 17c.
The sense of "a person's work, occupation, that which one does for a livelihood" is recorded late 14c. (in late Old English bisig appears as a noun with the sense "occupation, state of employment"). The sense of "that which is undertaken as a duty" is from late 14c. The meaning "what one is about at the moment" is from 1590s. The sense of "trade, commercial engagements, mercantile pursuits collectively" is attested by 1727, on the notion of "matters which occupy one's time and attention." In 17c. business also could mean "sexual intercourse."
Business card is attested from 1840; business letter from 1766. Business end "the practical or effective part" (of something) is American English, by 1874. Phrase business as usual attested from 1865. To mean business "be intent on serious action" is from 1856. To mind (one's) own business "attend to one's affairs and not meddle with those of others" is from 1620s.
1876, "artificial jargon of corrupted English with a few Chinese, Portuguese, and Malay words, arranged according to the Chinese idiom, used by the Chinese and foreigners for colloquial convenience in business transactions in the ports of China and the Far East," from pigeon English (1859), the name of the reduced form of English used in China for communication with Europeans, from pigeon, pidgin "business, affair, thing" (1826), itself a pidgin word (with altered spelling based on pigeon), representing a Chinese pronunciation of business. The meaning was extended by 1891 to "any simplified language."
computer programming language for use in business operations, 1960, U.S. Defense Department acronym, from "Common Business-Oriented Language."
early 15c., negotiacioun, "a dealing with people, trafficking," from Old French negociacion "business, trade," and directly from Latin negotiationem (nominative negotiatio) "business, traffic," noun of action from past participle stem of negotiari "carry on business, do business, act as a banker," from negotium "a business, employment, occupation, affair (public or private)," also "difficulty, pains, trouble, labor," literally "lack of leisure," from neg- "not" (from PIE root *ne- "not") + otium "ease, leisure," a word of unknown origin.
The sense expansion from "doing business" to also include "bargaining" about anything took place in Latin. Meaning "mutual discussion and arrangement of the terms of a transaction or agreement" is from 1570s.
"business house," 1744, according to Barnhart from German Firma "a business, name of a business," originally "signature," from Italian firma "signature," from firmare "to sign," from Latin firmare "make firm, affirm," in Late Latin, "confirm (by signature)," from firmus "strong; stable," figuratively "constant, trusty" (see firm (adj.)).