late 14c., "aspire or plan maliciously, agree together to commit a criminal or reprehensible act," from Old French conspirer (14c.), from Latin conspirare "to agree, unite, plot," literally "to breathe together," from assimilated form of com "with, together" (see con-) + spirare "to breathe" (see spirit (n.)), perhaps on the notion of "to agree (by spoken oath) to commit a bad act." Or perhaps the notion is "to blow together" musical instruments, i.e., "to sound in unison."
Neutral or good sense of "to contribute jointly to a certain result" is from 1530s. Related: Conspired; conspiring.
"one who plots or acts on evil or unlawful designs," c. 1400, conspiratour, from Old French conspirateur, from Latin conspiratorem (nominative conspiratorio), noun of action from past-participle stem of conspirare "to agree, unite, plot," literally "to breathe together" (see conspire).
Conspirer is attested from 1530s, from Anglo-French conspirour. Fem. form conspiratrice is from early 15c.; conspiratress is from 1760. Related: Conspiratory.
mid-14c., "a plotting of evil, unlawful design; a combination of persons for an evil purpose," from Anglo-French conspiracie, Old French conspiracie "conspiracy, plot," from Latin conspirationem (nominative conspiratio) "agreement, union, unanimity," noun of action from past-participle stem of conspirare "to agree, unite, plot," literally "to breathe together" (see conspire).
Earlier in same sense was conspiration (early 14c.), from French conspiration (13c.), from Latin conspirationem. An Old English word for it was facengecwis.
Conspiracy theory "explanation of an event or situation involving unwarranted belief that it is caused by a conspiracy among powerful forces" emerged in mid-20c. (by 1937) and figures in the writings of, or about, Charles Beard, Hofstadter, Veblen, etc., but the degree of paranoia and unreasonableness implied in each use is not always easy to discern. The phrase was used from 19c. in a non-pejorative sense "the theory that a (certain) conspiracy exists," especially in court cases. Its use in general reference to theories of hidden cabals pulling wires behind the scenes of national or global events is by 1871.
We shall better understand the ensuing civil war if we study the movements in the four most important of these States, in relation to a theory which asserts that the secession was a conspiracy whose central cabal, composed of Southern senators and representatives in Washington, dictated through its ramifications in the States the inception and the course of the revolution. [James Ford Rhodes, page headed "The Conspiracy Theory" in "History of the United States from the Compromise of 1850," New York, 1893]
To the Jingo Imperialist "the South African Conspiracy" is the alleged Dutch conspiracy to drive the British into the sea. But, to the man accustomed to weigh evidence and to base his opinions on ascertained facts, it is clear that this conspiracy theory is absolutely untenable, for whatever "evidence" has been adduced in support of the theory is nebulous and shadowy in the extreme. ["The South African Conspiracy," in The Westminster Review, January 1902]
"conspire in fraud or deception," 1520s, from Latin colludere "act collusively," literally "to play with" (see collusion). Related: Colluded; colluder; colluding.
1580s, "to make a map or diagram of, lay down on paper according to scale;" also "to lay plans for, conspire to effect or bring about" (usually with evil intent), from plot (n.). Intransitive sense of "to form a plan or device" is from c. 1600. Related: Plotted; plotter; plotting.
1590s (implied in colloguing) "to flatter, curry favor," a word of unknown origin; perhaps from French colloque "conference, consultation" (16c., from Latin colloqui "speak together;" see colloquy) and influenced by dialogue or colleague. Intransitive sense "to have a private understanding with, conspire, collude" is from 1640s.
late 14c., coniuracioun, "conspiracy, a plot, act of plotting" (senses now obsolete), also "a calling upon something supernatural, act of invoking by a sacred name, invocation of spirits, magic spell or charm," from Old French conjuracion "spell, incantation, formula used in exorcism" and directly from Latin coniurationem (nominative coniuratio) "a swearing together, conspiracy," in Medieval Latin "enchantment," noun of action from past-participle stem of coniurare "to swear together; conspire," from assimilated form of com "with, together" (see con-) + iurare "to swear," from ius (genitive iuris) "law, an oath" (see jurist).
late 13c., "command on oath;" c. 1300, "summon by a sacred name, invoke by incantation or magic," from Old French conjurer "invoke, conjure" (12c.) and directly from Latin coniurare "to swear together; conspire," from assimilated form of com "with, together" (see con-) + iurare "to swear," from ius (genitive iuris) "law, an oath" (see jurist).
The magical sense is from the notion of "constraining by spell" a demon to do one's bidding. Related: Conjured; conjuring. Phrase conjure up "cause to appear in the mind" (as if by magic) attested from 1580s.