άμπακας

Greek

An αντιδάνειο (antidáneio):^[1]^[2] From άμπακος (ámpakos) with a metaplasm of the ending to -ας (-as), inherited from Medieval Byzantine Greek ἄμπακος (ámpakos, “a plate with sand for writing at school”), from Italian abaco (“abacus”), from Latin abacus, from Ancient Greek ἄβαξ (ábax).
The sense "voracious, large quantity" from "he knows a lot, from using the abacus".

άμπακας • (ámpakas /ábakes/) m (plural άμπακες) usually in the singular

(figuratively) a lot, large quantity mainly used in the phrase:
τρώει τον άμπακα ― tróei ton ámpaka ― (s)he ate too much, s(he) is voracious

see also: περίδρομος (perídromos)
(obsolete sense, historical sense) abacus, as in the Medieval ἄμπακος, άβακας (ávakas)^[3]

Rare plural, especially genitive plural, with persitent accent as in foreign words (also found with recessive accent, αμπάκων).

^ άμπακος (αντιδάν.) - Babiniotis, Georgios (2010) Ετυμολογικό λεξικό της νέας ελληνικής γλώσσας Etymologikó lexikó tis néas ellinikís glóssas [Etymological Dictionary of Modern Greek language] (in Greek), Athens: Lexicology Centre
^ άμπακας (αντδ), in Λεξικό της κοινής νεοελληνικής [Dictionary of Standard Modern Greek], Triantafyllidis Foundation, 1998 at the Centre for the Greek language
^ άμπακος - Georgakas, Demetrius, 1908-1990 (1960-2009) A Modern Greek-English Dictionary [MGED online, 2009. letter α only (abbreviations)], Centre for the Greek language