With sightings being documented as far back as the 13th century (but most likely a giant squid) the Kraken is a legendary monster of the sea that supposedly hangs out in Norway and Greenland.
, despite various fictitious interpretations, the original sightings report the creature to be more crab-like than the massive ship-eating octopus we’ve come to imagine. The mile-long (not kidding) crab thing caused giant whirlpools and forced boats to burst up on a flying fountain of water coming from it’s nostrils! Zut alors!
The word Kraken translates to an unhealthy animal, or something twisted, in modern German, it translates to Octopus. In dutch, the words means breaking or the sound of crackling. Hmmm.
The phrase “release the Kraken” comes from the original Clash of the Titans movie in which the gods are angry and want to release this destructive beast upon the humans who have angered them.
There’s a great article with more information here: http://anomalyinfo.com/articles/sa00102.php