What is the history of a Shillelagh?

a short walking stick with a thickened "T" shape at the top. supposedly used more in fighting than in walking but I've never seen an actual one in Ireland - only in souvenir shops! said to be named after the little village of the same name in county wicklow.

Often the sticks were made from blackthorn roots, a very dense wood, and had a fist size knob instead of a "t" shape. Or, any other dense wood such as oak. Unfortunately, eventually the English nearly wiped out the oak forests for their ship builing needs. The shillelagh (which can have numerous pronounciations) could be long like a walking stick or sometimes short and worn in the belt. In more ancient times they were carried for protection, or were used in ritual type fighting with definite rules of conduct based on certain honor or codes. Though not as formal, and usually not ending in death, think of the Japanese sword fighting and the formal honors and codes of contact in that type of battle.