Klaus Stortebeker was a 14th century German privateer/pirate. Originally privateers were government approved pirates who only harrassed and stole from their home country's enemies.
It was a way to disrupt commerce and weaken the other guys chance for winning a lengthy war.
Klaus was a fairly good pirate and saw no reason to stop when his country officially asked him to.
They had been happy with his performance when he was focused on the Danes (f@#ing Danes) but when he started screwing with the Hanseatic League, who were the wealthy trading merchants of the area, things got tough.
Eventually, Klaus & Crew were captured and sentenced to death.
Klaus, in an attempt to save some of his crew, made a last minute bargain with his captors.
They would free however many of the men that Klaus's headless body could walk past after the axman did his deed.
He walked past eleven.
More here at Atlas Obscura -
http://www.atlasobscura.com/places/impaled-skull-of-klaus-stortebeker-pirate-walking-corpse
There's even a dramatic reenactment (in German) here. Pretty cool stuff.
http://www.myvideo.de/watch/5711742/Stoertebeker_2_teil_part_11_11
http://www.executedtoday.com/2010/10/20/1401-klaus-stortebeker-victual-brothers-pirate/
There's even Stortebecker poetry!
Klaus Störtebecker is our master
advised by Godeke Michels!
Shoot through the waves like storm, just faster
The Flying Dutchman’s godfather
Gaffer is the ships goblin
Let’s tackle, crew!
Life is bauble!
We are the hell of Helgoland
Our bloody flag is cracking the mast
Rats scurrying on the floor
A skeleton is our guest
On the sail there are strange shadows
The mermaid is swimming in our wake
Laugh, crew!
Life is bauble!
Still ruling is the hell of Helgoland
And when our ship makes its last run
Laugh while like a coffin she goes down
We die an ancient pirate’s way
Today we fight, tomorrow we drown
In green algae and white sand
Land ho, crew, land!
Life is bauble!
Such dies the hell of Helgoland
-Folk song honoring Klaus Stortebeker
Also, Stortebeker is a "nom de guerre" which translates roughly to "one who can down a four litre mug in one gulp".