The island has been habitant for a long time. Its most earliest name, Augia or Andium, was given to it by a French king in 550. The island was seized by a duke of Normandy, a French province in 933. From then to around 1200, Normandy and England have fought, conquered, reconquered, split and fought a lot. Jersey was born in 1204, after becoming property of the English Crown when it separated from Normandy. Jersey had gained informal independence, yet still relying on England for protection.
In the 18th century, Jersey was on high alert due to political tensions between Britain and France. During the American Wars of Independence, there were two invasion attempts: one in 1779 was stopped, and another on January 6, 1781, briefly succeeded when a Frenchman captured St Helier, but he was defeated by Major Francis Peirson in the Battle of Jersey. After a short period of peace, Jersey was affected by the French Revolutionary and Napoleonic Wars. These events are known as the Battle of Jersey.
While staying away from conflict in WW1, Jersey and her siblings were occupied by Germany from 1940 to 1945. The islands were liberated on 9 May 1945, which is still celebrated as their Liberation Day and birthday.
Hetalia-ified source: History of Jersey, Jersey on Wikipedia.