Second a domain name must be appealing to users. Oh well, it should be, at least.
I would go from this considerations:
- is it a brand you want to etsablish? Then I would suggest perhaps not to translate the domain name at all, but just register the same under local TLDs, like .de, .fr etc.
- do you want the keyword in the domain name, try to find out what the best keyword in that language would be.
Caution is advised: the translation you choose may carry cultural or idiomatic baggage in the new language. Apocryphally, Coca-Cola's "Come Alive" 1950s ad campaign was mistranslated to "Brings Your Ancestors Back from the Dead" in Taiwan.
heini provided you with some very good awswer and choster raised an important point.
I live in Québec where people speak French (well, some kind of French). Cultural differences whithin the same language can have a serious impact on results. For instance is a French person from France wants to buy a new house, he will type completely different key phrases than a French person from here. I guess this can be duplicate to other languages too.