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.
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.