advantageyoudaoicibaDictYouDict[advantage 词源字典]
advantage: [14] Advantage comes from Old French avantage, which was based on avant ‘before’; the notion behind its formation was of being ahead of others, and hence in a superior position. As with advance, the intrusive -dbecame established in the 16th century, on the analogy of words genuinely containing the Latin prefix ad-. The reduced form vantage actually predates advantage in English, having entered the language via Anglo-Norman in the 13th century.
[advantage etymology, advantage origin, 英语词源]
advantage (n.)youdaoicibaDictYouDict
early 14c., avantage, "position of being in advance of another," from Old French avantage "advantage, profit, superiority," from avant "before," probably via an unrecorded Late Latin *abantaticum, from Latin abante (see advance).

The -d- is a 16c. intrusion on the analogy of Latin ad- words. Meaning "a favoring circumstance" (the opposite of disadvantage) is from late 15c. Tennis score sense is from 1640s, first recorded in writings of John Milton, of all people. Phrase to take advantage of is first attested late 14c.