Expert
Middle English (as an adjective): from French, from Latin expertus, past participle of experiri ‘try’. The noun use dates from the early 19th century Compare with experience and experiment.
wiktionary
From Old French, from Latin expertus.
etymonline
expert (adj.)
late 14c., "having had experience; skillful," from Old French expert, espert "experienced, practiced, skilled" and directly from Latin expertus (contracted from *experitus), "tried, proved, known by experience," past participle of experiri "to try, test," from ex "out of" (see ex-) + peritus "experienced, tested," from PIE *per-yo-, suffixed form of root *per- (3) "to try, risk." The adjective tends to be accented on the second syllable, the noun on the first. Related: Expertly; expertness.
expert (n.)
early 15c., "person wise through experience," from expert (adj.). The word reappeared 1825 in the legal sense, "person who, by virtue of special acquired knowledge or experience on a subject, presumably not within the knowledge of men generally, may testify in a court of justice to matters of opinion thereon, as distinguished from ordinary witnesses, who can in general testify only to facts" [Century Dictionary].
