The Power name was originally de la Poer. De la Poer fought alongside Rossiter and William the Coqueror in 1066 at the Battle of Hastings. Descendants of these two families went to Ireland in 1169 with Strongbow. A good reference book is "Irish Pedigrees" by O'Hart. The Power family motto is "per crucem ad coronam" - "by the Cross to a crown"