"having knowledge;" in law, "competent to take legal or judicial notice," 1744, back-formation from cognizance.
Latin phrase, literally "I think, therefore I am;" the starting point of Cartesian philosophy (see Cartesian), from cogito, first person singular present indicative active of cogitare "to think" (see cogitation) + ergo "therefore" (see ergo) + sum, first person singular present indicative of esse "to be" (from PIE root *es- "to be").
mid-14c., conisance, "device or mark by which something or someone is known," from Anglo-French conysance "recognition," later, "knowledge," from Old French conoissance "acquaintance, recognition; knowledge, wisdom" (Modern French connaissance), from past participle of conoistre "to know," from Latin cognoscere "to get to know, recognize," from assimilated form of com "together" (see co-) + gnoscere "to know" (from PIE root *gno- "to know").
Meaning "knowledge by observation or notice, understanding, information" is from c. 1400. In law, "the exercise of jurisdiction, the right to try a case" (mid-15c.). Meaning "acknowledgment, admission" is from 1560s. The -g- was restored in English spelling 15c. and has gradually affected the pronunciation, which was always "con-." The old pronunciation lingered longest in legal use.
1590s, Conniacke wine, "wine produced in Cognac," the region in western France. The sense of "brandy of a superior quality distilled from wines produced in the Cognac region" is from 1680s as Cognac brandy; by 1755 simply as Cognac. Also sometimes used generally of any brandy of good quality. The place name is from Medieval Latin Comniacum, from the personal name Cominius and the Gallo-Roman suffix -acum.
mid-15c., "heraldic mark;" 1530s, "knowledge, act or state of knowing," abstract noun from the past-participle stem of Latin cognoscere "to get to know, recognize" (see cognizance, which is now the usual word).