First of all, define what pirates you're talking about. Like hellheaven indicated, pirates existed in a huge number of times and places, like the Vikings or Cilician pirates in antiquity. Secondly, you should be wary of grouping even such pirates together, as they most likely had no loyalties outside their own ship or group.
For ideas (1000 words is really short btw):
-Role of privateers in the Anglo-French wars.
-Role of pirates in technological advancements. For instance, in ship types: Dunkirk privateers evolved the frigate, a very important technological advancement.
-Was there a pirate code of conduct (with which you could relate the Romantic ideas of pirates) and did they adhere to an idea of just war?
For sources I'd suggest you google some Osprey books, for a 1000 word essay the quality might suffice, and it's always convenient to check their source material.
Good luck!
PS see if you can find this book on the internet:
http://www.ospreypublishing.com/stor...9781855327061/ (google it with the right keywords)