Those scholars who suggest a link between the giant and Hercules are in favour of a Roman antiquity to the figure but I believe that it is much older and more native than this. The Dagda, the primary God of the Irish-Celtic mythology would be a better fit for the evidence. The Dagda was a supreme and protective deity and He is renown for His iron club and cauldron which is a possible source for the Holy Graal, an object plagiarised and misrepresented by the xtian church. The Dagda was known as the All-Father and here we are reminded of the Germanic All-Father Woden. In Irish mythology The Dagda became chief of the Tuatha De Danann after the loss of Nuada`s hand in battle. We are again reminded of a similar event in Germanic mythology. The once supreme Tiw was replaced by Woden and Tiw also lost His hand, not in battle but as a sacrifice to restrain the Fenris Wolf. It would seem that both mythologies are representing a similar Aryan event, the eclipse of one Sky God by another.
However scholars tend to equate Woden more with Lugh. Like Woden Lugh also carried a formidable magic spear and was connected with ravens. Lugh used magic and as with Woden He is known to have had either one eye or used a one eyed magical technique. Thunor on the other hand has a closer parallel with The Dagda. Like Tiw, Thunor once held supreme position amongst the other Germanic Gods but in many Germanic lands was later eclipsed by Woden. Thunor`s thunder weapon was generally held to be an axe like the Baltic and Slavic counterparts. This axe later evolved into the hammer. Sometimes images or amulets are indistinguishable between the two. However it is less well known that He is also associated with a club. Indeed in the Rhineland Donar is more associated with the club than an axe or hammer. Some scholars postulate that this is because of cultural contact and exchange with the Romans. However this can not be the case with The Dagda and there is reason to believe that this weapon was common to both the Celtic and Germanic Thunder God at an early stage. In a sense this represents the series of development of weapons and tools through prehistory to historical times.
Donarkeule[Donar Clubs] were popular in Anglo-Saxon Britain and examples have been found with `hailstone` markings. Significantly no such finds have been unearthed in Scandinavia. [See The Divine Thunderbolt. Missile of the Gods by J.T. Sibley, 2009]. If the giant does have an origin which goes no further back than the Roman occupation of southern Britain then it could just as easily represent the God Donar as Hercules for we know that German mercenaries did serve Rome and they could be responsible for the creation of this chalk figure.
The enlarged phallus of the giant along with the club signifies a fertilty role and we know that Thunor`s hammer was a fertility symbol as well as a weapon. We are reminded of the story of the loss of Thor`s hammer in Thrymskvida in the Elder Edda in which the hammer is placed in the lap of the `bride`[Thor] as part of the marriage ceremony. This symbolism continues on into folklore:
"In Scandinavia the union of man and wife was anciently consecrated by laying Thor`s symbol, the hammer, in the brides`s lap; and Thursday is still regarded as an auspicious day for marrying. In Germany, where Christian tradition has partially identified Thor with the devil, it is held unlucky to marry on that day.
"In a wood near Dahle there was formerly a great oak tree (now reduced to a stump) to which new married couples used to repair, dance round it three times, and cut a cross upon it. This cross betokened of yore Thor`s hammer, the consecrator of marriage."[Curiosites of Indo-European Folk-lore, Walter Keating Kelly, 1863]
The Dagda seems to be a God that was limited to Ireland and not pan-Celtic. Celtic mythology is replete with hundreds of local deities so I would contend that the Cerne Abbas Giant is more likely to have his origins in Donar than either The Dagda or Hercules.