The Dagda is an important god of Irish mythology. His name means "The Good God", (Old Irish- "deagh dia"; Mod. Irish- "dea-Dia") not good in a moral sense, but good at everything, or all-powerful. The Dagda is a father-figure (he is also known as Eochaid Ollathair, or Eochaid All-Father) and a protector of the tribe. In some texts his father is Elatha, in others his mother is Ethlinn.
Irish tales depict The Dagda as a figure of immense power, armed with a magic club and associated with a cauldron. The club was supposed to be able to kill nine men with one blow; with the handle he could return the slain to life. The cauldron was bottomless, capable of feeding an army. He also possessed a richly ornamented magic harp made of oak which, when the Dagda played it, put the seasons in their correct order; other accounts tell of the harp being used to command the order of battle. He possessed two pigs which could be cooked and eaten, but would remain whole, alive and undiminished, and ever-laden fruit trees.
The Dagda was moreover the High King of the Tuatha Dé Danann, the supernatural beings who inhabited Ireland prior to the coming of the Celts. His lover was Boann and his wife was Breg. Prior to the battle with the Fomorians, he coupled with the goddess of war, the Morrigan, on Samhain in exchange for a plan of battle.
Despite his great power and prestige, the Dagda is sometimes depicted as oafish and crude, even comical, wearing a short, rough tunic that barely covers his rump, dragging his great penis on the ground.
The Dagda had an affair with Boann, wife of Nechtan. In order to hide their affair, Dagda made the sun stand still for nine months; therefore their son, Aengus, was conceived, gestated and born in one day. He, along with Boann, helped Aengus search for his love.
The Dagda was also the father of Bodb Dearg, Cermait, Midir, Aine and Brigit. He was the brother or father of Ogma, who is probably related to the Gaulish god Ogmios; Ogmios, depicted as an old man with a club, is one of the closest Gaulish parallels to the Dagda. Another Gaulish god who may be related to the Dagda is Sucellos, the striker, depicted with a hammer and cup.
He is credited with an eighty-year reign over the Tuatha Dé Danann, before dying at the Brú na Bóinne (Newgrange}, finally succumbing to poison administered by Cethlenn during the first battle of Magh Tuiredh.
The Cerne Abbas giant, a famous outline of an ithyphallic giant with a club cut into the chalky soil at Cerne Abbas, in Dorset, England, was probably produced in Roman times, but may represent the Dagda.
Cerne Abbas giant (http://www.sacredsites.com/europe/england/cerne_giant.html)