"soft, sweet paste made of melted chocolate and cream," 1962, from Italian, the thing itself is said by Ayto ["Diner's Dictionary"] to have been created in Paris c. 1850; the name is of unknown origin. It is attested 19c. as the name of a kind of garment and an insult ("blockhead").

1570s, "what someone says," hence "what one has in him to say, a declaration or statement," from say (v.). The Old English noun secge meant "speech."

The meaning "right or authority to be heard in a matter or influence a decision" is from 1610s in have a say; earlier in this sense was have a saying (late 15c.). Extended form say-so "personal assertion" is recorded by 1630s; in the sense of "power, authority" it is by 1896. 

1795; Figurative use by 1841. Hair perhaps in reference to the slight pressure required to activate it.

The difference between a hair-trigger and a common trigger is this—the hair-trigger, when set, lets off the cock by the slightest touch, whereas the common trigger requires a considerable degree of force, and consequently is longer in its operation. [Charles James, "Military Dictionary," London, 1802]

late 14c., "refraining from undue indulgence," especially in reference to food and drink, from Old French abstinent (earlier astenant) "moderate, abstemious, modest," from Latin abstinentem (nominative abstinens) "temperate, moderate," present participle of abstinere, abstenere "withhold, keep back, keep off," from assimilated form of ab "off, away from" (see ab-) + tenere "to hold" (from PIE root *ten- "to stretch").

1967 (earlier narco, 1960), American English slang, shortened form of narcotics agent. It had been used 1955 for narcotics hospital, 1958 for narcotics addict. The senses and spelling have tended to merge with older but unrelated nark (q.v.).

late 14c., originally in grammar (in reference to certain nouns that do not name concrete things), from Latin abstractus "drawn away," past participle of abstrahere "to drag away, detach, pull away, divert;" also figuratively, from assimilated form of ab "off, away from" (see ab-) + trahere "to draw," from PIE root *tragh- "to draw, drag, move" (see tract (n.1)).

The meaning in philosophy, "withdrawn or separated from material objects or practical matters" (opposed to concrete) is from mid-15c. That of "difficult to understand, abstruse" is from c. 1400.

In the fine arts, "characterized by lack of representational qualities" by 1914; it had been a term in music at least since 1847 for music without accompanying lyrics. Abstract expressionism as an American-based uninhibited approach to art exemplified by Jackson Pollock is from 1952, but the term itself had been used in the 1920s of Kandinsky and others.

Oswald Herzog, in an article on "Der Abstrakte Expressionismus" (Sturm, heft 50, 1919) gives us a statement which with equal felicity may be applied to the artistic attitude of the Dadaists. "Abstract Expressionism is perfect Expressionism," he writes. "It is pure creation. It casts spiritual processes into a corporeal mould. It does not borrow objects from the real world; it creates its own objects .... The abstract reveals the will of the artist; it becomes expression. ..." [William A. Drake, "The Life and Deeds of Dada," 1922]

Then, that art we have called "abstract" for want of any possible descriptive term, with which we have been patient, and, even, appreciative, getting high stimulation by the new Guggenheim "non-objective" Art Museum, is reflected in our examples of "surrealism," "dadaism," and what-not, to assert our acquaintance in every art, fine or other. [Report of the Art Reference Department of Pratt Institute Free Library for year ending June 30, 1937]