Learn English – Term for a word with opposite meaning to its root

At your source (etymonline for greed), if you enter gher or gher- or *gher- as the search term you can find other words that stem, eventually, from Indo-European root *gher- in its sense to like, want, such as Eucharist, yearn, hortatory, charisma.

Note that PIE *gher- is shown in etymonline with several additional senses:
• “to scrape, scratch” in the etymologies of gash and character
• “to bristle” for arugula and urchin
• “to grasp, enclose” for cohort, chorus, yard
• “to call out” for greet

This phenomenon is generally called an "ellipsis". But this word can also be used to describe a typographical sequence of three dots ("..."), often used to indicate missing speech rather than describe an incomplete saying.

If you want to be more precise (and technical) and avoid confusion, you can use the word "anapodoton".

UPDATE

Thought you might like some more examples: http://en.wiktionary.org/wiki/Appendix:English_examples_of_anapodoton