1520s, "something that frightens, a scarecrow;" 1540s, "sudden panic, sudden terror inspired by a trifling cause, false alarm," from scare (v.). The earlier form was Middle English sker "fear, dread, terror, fright" (c. 1400). Scare tactic "attempt to manipulate public opinion by exploitation of fear" is by 1948.
1590s, "frighten, terrify suddenly," an unusual alteration of Middle English skerren "to frighten" someone (late 12c.), from Old Norse skirra "to frighten; to shrink from, shun; to prevent, avert," which is related to skjarr "timid, shy, afraid of," but of unknown origin.
In Scottish also skair, skar, which seem to track closer to the word's expected development, and in dialect skeer, skear. Intransitive meaning "become frightened, be scared" is from 14c.; the specific sense of "be alarmed by rumor" is from 1900.
To scare away "drive off by frightening" is from 1650s. To scare up "procure, obtain, find, bring to light" is recorded by 1846, American English, from notion of rousing game from cover. Related: Scared; scaring.
mid-15c., "frightened, alarmed, startled," past-participle adjective from scare (v.). Emphatic scared stiff is recorded by 1900; scared shitless by 1936. Scaredy-cat "timid person" first attested 1906.
also scarey, "terrifying, causing or tending to cause fright," 1580s, from scare (n.) + -y (2). Meaning "easily frightened, subject to scares" is from 1800. In this sense formerly sometimes colloquially as skeery, skeary; OED marks this meaning as originally and chiefly North American. Related: Scarier; scariest.
1550s, from scare (v.) + crow (n.). Earliest reference is to a person employed to scare birds. Meaning "figure of straw and old clothes made to resemble a person and set in a grain field or garden" to frighten crows and other birds from the crop is implied by 1580s; hence "gaunt, ridiculous person" (1590s). For the formation, compare daredevil.
An older name for such a thing was shewel. Shoy-hoy apparently is another old word for a straw-stuffed scarecrow (Cobbett began using it as a political insult in 1819 and others picked it up; OED defines it as "one who scares away birds from a sown field," and says it is imitative of their cry). Also fray-boggard (1530s). Middle English had skerel, apparently in the same sense, from skerren "scare."
1650s, "general science or theory of the material universe as an ordered whole," from Modern Latin cosmologia, from Greek kosmos (see cosmos) + -logia "discourse" (see -logy). By 1753 as "the branch of metaphysics which discusses the ultimate philosophical problems relating to the existence of the universe." Related: Cosmologist.
They cannot scare me with their empty spaces
Between stars—on stars where no human race is.
I have it in me so much nearer home
To scare myself with my own desert places.
[Robert Frost, from "Desert Places," 1936]