What does Brand mean?
From the Old Norse 'brandr', which meant both 'firebrand' (a burning piece of wood) and, by extension, 'sword blade'. The fire sense is the original one; the name is sometimes glossed 'sword' for the derived meaning.
What does Jormungandr mean?
Old Norse Jormungandr, the Midgard/World Serpent that encircles the earth. From jormun- 'huge, vast' + gandr, an ambiguous word covering 'serpent/staff/magical being', commonly read 'giant serpent'. Flag: a mythological serpent's NAME, and the second element is genuinely ambiguous (also 'giant staff/binding'), so the 'serpent' reading is the usual but not the only one.