I don't understand your question. Packrat means hoarder. Therefore, translations for it will be the same as translations for hoarder. There is no reason why they should be different. And there is no literal translation either.
Packrat is also another word for woodrat. I've found that its official name is Neotoma, Νεότομα in Greek, but you will find that neither the animal nor its name is known to Greeks.
The pack rat is an american animal. In Europe, there is the hamster. In German, there is "hamstern" as a verb to express excessive collecting of things (and "Hamsterer" for the person who does it). But I don't know if there is an equivalent in Greek.