early 15c., "a sign, that which indicates," from Latin indicationem (nominative indicatio) "an indicating; valuation," noun of action from past participle stem of indicare "point out, show," from in- "into, in, on, upon" (from PIE root *en "in") + dicare "proclaim" (from PIE root *deik- "to show," also "pronounce solemnly," and see diction).
1660s, "that which indicates or points out," from Late Latin indicator, agent noun from indicare "to point out, show" (see indication). As a finger muscle, from 1690s. As a steam-cylinder's pressure gauge, 1839. As a device on a motor vehicle to signal intention to change direction, 1932.
mid-15c., "that points out, states, or declares" (grammatical), from Old French indicatif (14c.), from Late Latin indicativus "serving to point out," from indicat-, past participle stem of Latin indicare "to point out, show" (see indication). The "mood in the conjugation of a Latin verb whose essential function is to state a fact (as opposed to a wish, supposition or command)" [The Middle English Compendium]. Related: Indicatively.
1650s, "to point out," back-formation from indication (q.v.) or else from Latin indicatus, past participle of indicare "to point out, show," from in- "into, in, on, upon" (from PIE root *en "in") + dicare "proclaim" (from PIE root *deik- "to show," also "pronounce solemnly," and see diction). Especially "to give suggestion of, be reason for inferring" (1706). Related: Indicated; indicating.
Proto-Indo-European root meaning "to show," also "pronounce solemnly," "also in derivatives referring to the directing of words or objects" [Watkins].
It forms all or part of: abdicate; abdication; addict; adjudge; apodictic; avenge; benediction; betoken; condition; contradict; contradiction; dedicate; deictic; deixis; dictate; diction; dictionary; dictum; digit; disk; ditto; ditty; edict; Eurydice; index; indicate; indication; indict; indiction; indictive; indite; interdict; judge; judicial; juridical; jurisdiction; malediction; malison; paradigm; policy (n.2) "written insurance agreement;" preach; predicament; predicate; predict; prejudice; revenge; soi-disant; syndic; teach; tetchy; theodicy; toe; token; valediction; vendetta; verdict; veridical; vindicate; vindication; voir dire.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit dic- "point out, show;" Greek deiknynai "to show, to prove," dike "custom, usage;" Latin dicere "speak, tell, say," digitus "finger," Old High German zeigon, German zeigen "to show," Old English teon "to accuse," tæcan "to teach."
"to give indication of the future," 1775, from omen (n.). Related: Omened. The Latin verb ominari meant "to know or tell from omens, to predict."
"indication, pointing out," 1949, in grammar, from Greek deixis "reference," from deiknynai "to show" (from PIE root *deik- "to show"). Related: Deictic.