Origin and history of *ant-

mid-13c., avauncen (transitive), "improve (something), further the development of," from Old French avancir, avancier "move forward, go forward, set forward" (12c., Modern French avancer), from Vulgar Latin *abanteare (source of Italian avanzare, Spanish avanzar). This is from Late Latin abante "from before," composed of ab "from" (see ab-) + ante "before, in front of, against" (from PIE root *ant- "front, forehead").

Compare French avant "before" (as in avant-garde), which is from the same Late Latin word. The unetymological -d- in English was inserted 16c. on the mistaken notion that initial syllable was from Latin ad-.

It is attested from c. 1300 as "to promote, raise to a higher rank." The intransitive sense of "move forward, move further in front" is by mid-14c.; the transitive meaning "bring forward in place, move (something) forward" is from c. 1500. The meaning "give (money, etc.) before it is legally due" is attested by 1670s. Related: Advanced; advancing. The adjective (in advance warning, etc.) is recorded from 1843.

early 14c., avantage, "position of being in advance of another," from Old French avantage "advantage, profit; superiority" (12c.), from avant "before," probably via an unrecorded Late or Medieval Latin *abantaticum, from Latin abante "from before," composed of ab "from" (see ab-) + ante "before, in front of, against" (from PIE root *ant- "front, forehead"). Compare advance (v.).

Advantage is the possession of a good vantage-ground for the attainment of ulterior objects of desire .... [Century Dictionary]

The unetymological -d- is a 16c. intrusion on the analogy of the many Latin ad- words in English. The meaning "any condition favorable to success, a favoring circumstance" (the opposite of a disadvantage) is from late 15c. The tennis score sense is from 1640s (in the writings of John Milton). Phrase take advantage of is from late 14c. as "avail oneself of," also "impose upon." To have the advantage of (someone) "have superiority over" is from 1560s.