What does Jordan mean?
From the River Jordan, Hebrew Yarden, derived from the root y-r-d 'to go down, descend, flow down' - describing the river's descent. Long used as a given name, originally for those baptised in or with water from the Jordan.
What does Leviathan mean?
Hebrew livyathan, a great sea-serpent/monster, generally glossed 'twisted, coiled' and derived (per Gesenius) from the root l-w-h 'to twine, wind' with a suffix, i.e. 'wreathed one'. Flag: the derivation is disputed (some hold it a loanword), and in use it is the name of a biblical serpent-monster; the 'coiled serpent' sense is the established reading.