Old English grædig (West Saxon), gredig (Anglian) "voracious, hungry," also "covetous, eager to obtain," from Proto-Germanic *grædagaz (source also of Old Saxon gradag "greedy," Old Norse graðr "greed, hunger," Danish graadig, Dutch gretig, Old High German gratag "greedy," Gothic gredags "hungry"), from *græduz (source also of Gothic gredus "hunger," Old English grædum "eagerly"), possibly from PIE root *gher- (2) "to like, want" (source of Sanskrit grdh "to be greedy").
In Greek, the word was philargyros, literally "money-loving." A German word for it is habsüchtig, from haben "to have" + sucht "sickness, disease," with sense tending toward "passion for."
-ly 2
common adverbial suffix, forming from adjectives adverbs signifying "in a manner denoted by" the adjective, Middle English, from Old English -lice, from Proto-Germanic *-liko- (cognates: Old Frisian -like, Old Saxon -liko, Dutch -lijk, Old High German -licho, German -lich, Old Norse -liga, Gothic -leiko); see -ly (1). Cognate with lich, and identical with like (adj.).
Weekley notes as "curious" that Germanic uses a word essentially meaning "body" for the adverbial formation, while Romanic uses one meaning "mind" (as in French constamment from Latin constanti mente). The modern English form emerged in late Middle English, probably from influence of Old Norse -liga.