There is Old Norse sultr, Icelandic sultur (“starvation”) and Old English swylt (“death”); both seem to be zero-grade. Do we know enough about Crimean Gothic phonology to tell whether schwalth is o-grade (< *swaltaz) or whether -wa < *-u-? If the latter, it could be the same as the Old Norse word.
I think sult is the West Norse form, Modern Swedish has svält. It's also possible that it's not a direct descendant of the original nominal form, but and independent creation from the verb, I guess. Thank you for your reply, anyway.
@Wakuran: Modern Swedish does have svält (Old Swedish svælter), which is indeed probably influenced by the verb form svälta (Old Swedish svælta); but older Swedish also has sylt (Old Swedish sulter, sylt and sylter) and Danish has sult. I have now discovered, however, that Swedish also has an obsolete svalt (Old Swedish svalter), which does seem to be < *swaltaz.