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.
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."
in writing, to indicate the common casual pronunciation of could have, by 1909.
"financial losses, the debit side of an account," 1929, from the red ink traditionally used to indicate debits in accounts. Earlier, "cheap wine" (1919).
"short horizontal line placed over a vowel to indicate length," 1827, from Latinized form of Greek makron, neuter of makros "long" (from PIE root *mak- "long, thin").