"The thief is greedy for the cookies."
Translation:Fur crustula concupiscit.
They choose it because it expresses a really strong desire. You can be "greedy for money", "greedy for power".
Collins dictionary, Oxford dictionary, and Cambridge dictionary,
have all a page for "greedy for", so I guess it's English.
To desire is not as strong as to be greedy for something, according to the definitions of both words, to be greedy is to desire more and more and more...
To desire is simply to want to possess something (strongly), but "to be greedy for" is:
wanting more money, power, food, etc. than you really need
Etymology: Old English grǣdig, of Germanic origin.
Concuspiciencia means longing, concuspicence.
To covert is said to be from the old French "couvert" in Etymologyonline, but I don't think this etymology is accurate, as it's hard to see the link between couvert (hidden) and covert. ( Edit: indeed, It seems to be a different "covert". There's 2 "covert" words in English, both derivating from French, but not the same French word (convoit, et couvert) but both gave the same English form "covert" oddly.)
Here, it's rather come from Old French coveitier (modern French "convoiter"), from latin cupio (to desire, same root than "concupisciencia"), same meaning than covet.
So, I think "covet" is right, but I don't know if it is as strong as "to be greedy for something."
French convoitise from the same etymology than covert, is a strong word.
Yes, you can be greedy for money or power, but not for concrete things, at least not in common parlance. "I am greedy for her jewels" would never be used by an adult native speaker. That would usually be expressed in speech as "I want her jewels". In writing you would also see "I covet her jewels" or "I desire her jewels".