What does the red hand on the Tyrone flag mean?

Eoghain O'Neill, a high King of Ulster was battling a Scottish Chieftan for possession of land. The battle was at sea and the winning condition dictated that whoever should place their hand on the piece of land first would be the owner. O'Neill knew he was losing the race so in order to win the land he cut off his hand and threw it onto the land. The hand was red from his blood - hence 'the red hand of Ulster', which appears on the flag.